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Delprat-Jannaud, Florence. „Le captage et le stockage du CO2“. Reflets de la physique, Nr. 77 (Februar 2024): 78–85. http://dx.doi.org/10.1051/refdp/202477078.
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Le captage et le stockage géologique du gaz carbonique ne sont pas des technologies nouvelles : le captage et la séparation du CO2 sont appliqués dans l’industrie depuis des décennies, et l’injection de CO2 est pratiquée depuis les années 1970 pour la récupération assistée du pétrole. Toutefois, des verrous restent à lever pour leur déploiement à grande échelle. Cet article propose une revue des technologies existantes, qu’elles soient matures ou en cours de développement, ainsi qu’une discussion sur les enjeux à adresser : réduction des couts et de la pénalité énergétique pour le captage du CO2, mutualisation des infrastructures pour le transport, démonstration de la faisabilité du stockage massif ainsi que perspectives en matière d’utilisation.
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Berthod, Alain, Jun Xiang, Serge Alex und Colette Gonnet-Collet. „Chromatographie à contre courant et micelles inverses pour la séparation et l'extraction de cations métalliques“. Canadian Journal of Chemistry 74, Nr. 2 (01.02.1996): 277–86. http://dx.doi.org/10.1139/v96-031.
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Countercurrent chromatography (CCC) is a separation technique in which the stationary phase is a liquid. Diethylhexyl phosphoric acid (DEHPA) forms reverse micelles in heptane. Metallic ions, located in an aqueous phase, can be extracted into the aqueous core of the reverse micelles in the heptane phase. A CCC apparatus can be considered as a powerful mixing and extracting machine with efficiency above several hundreds of theoretical plates. La3+, Ce3+, Pr3+, and Nd3+ lanthanide cations were separated using CCC with a DEHPA-containing heptane stationary phase. Studying the retention variations with aqueous mobile phase pH, it was possible to determine the lanthanide extraction constants and separation coefficients. Overloading conditions are described. Frontal chromatography was performed using a Co2+ and Ni2+ solution. The Co2+ ions were concentrated in the heptane + DEHPA stationary phase, a part of the solution was deionized, and another part was enriched in only Ni2+ ions. This method also produced the extraction constants and separation coefficients. The use of CCC with a complexing stationary phase can be applied to any cation for ion filtering and concentration, or for deionization of aqueous phases. Key words: countercurrent chromatography, CCC; ion extraction, ion filtering, deionization, lanthanides, transition metals.
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Jean-Baptiste, Philippe, und René Ducroux. „Potentiel des méthodes de séparation et stockage du CO2 dans la lutte contre l'effet de serre“. Comptes Rendus Geoscience 335, Nr. 6-7 (Juni 2003): 611–25. http://dx.doi.org/10.1016/s1631-0713(03)00086-5.
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Kukulka, Wojciech, Krzysztof Cendrowski, Beata Michalkiewicz und Ewa Mijowska. „Correction: MOF-5 derived carbon as material for CO2 adsorption“. RSC Advances 9, Nr. 59 (2019): 34349. http://dx.doi.org/10.1039/c9ra90077b.
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Jinzhang, Jia, und Xiao Lingyi. „Retraction: Research on CO2/CH4/N2 competitive adsorption characteristics of anthracite coal from Shanxi Sihe coal mine“. RSC Advances 14, Nr. 52 (2024): 38581. https://doi.org/10.1039/d4ra90145b.
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Retraction of ‘Research on CO2/CH4/N2 competitive adsorption characteristics of anthracite coal from Shanxi Sihe coal mine’ by Jia Jinzhang et al., RSC Adv., 2024, 14, 3498–3512, https://doi.org/10.1039/D3RA08467A.
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Kottititum, Bundit, Thongchai Srinophakun, Niwat Phongsai und Quoc Tri Phung. „Optimization of a Six-Step Pressure Swing Adsorption Process for Biogas Separation on a Commercial Scale“. Applied Sciences 10, Nr. 14 (08.07.2020): 4692. http://dx.doi.org/10.3390/app10144692.
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Pressure swing adsorption (PSA) appears to be an effective technology for biogas upgrading under different operating conditions with low greenhouse gas emissions. This study presents the simulation of biomethane adsorption with the adsorption bed filled with a carbon molecular sieve (CMS). A six dual-bed six-step PSA process was studied which produced a high purity of biomethane. The design of the adsorption bed was followed by the real process of which the biomethane capacity was more than 5000 Nm3/h. For the adsorbent, a CMS-3K was used, and a biomethane gas with a minimum 92% purity was produced at 6.5 bar adsorption pressure. To understand the adsorption characteristics of the CH4 and CO2 gases, the Langmuir isotherm model was used to determine the isotherm of a mixed gas containing 55% CH4 and 45% CO2. Furthermore, the experimental data from the work of Cavenati et al. were used to investigate the kinetic parameter and mass transfer coefficient. The mass transfer coefficients of two species were determined to be 0.0008 s−1 and 0.018 s−1 at 306 K for CH4 and CO2, respectively. The PSA process was then simulated with a cyclic steady state until the relative tolerance was 0.0005, which was then used to predict the CH4 and CO2 mole fraction along the adsorption bed length at a steady state. Moreover, the optimal conditions were analyzed using Aspen Adsorption to simulate various key operating parameters, such as flowrate, adsorption pressure and adsorption time. The results show a good agreement between the simulated results and the real operating data obtained from the company REBiofuel. Finally, the sensitivity analysis for the major parameters was presented. The optimal conditions were found to be an adsorption pressure of 6 bar, an adsorption time of 250 s and a purity of up to 97.92% with a flowrate reducing to 2000 Nm3/h. This study can serve as a commercial approach to reduce operating costs.
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Lin, Wenjuan, Guo-Qing Tang und Anthony R. Kovscek. „Sorption-Induced Permeability Change of Coal During Gas-Injection Processes“. SPE Reservoir Evaluation & Engineering 11, Nr. 04 (01.08.2008): 792–802. http://dx.doi.org/10.2118/109855-pa.
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Summary Our study has two features. First, laboratory experiments measured the change of the permeability of coal samples as a function of pore pressure and injected-gas composition at constant effective stress. Second, adsorption-solution theory described adsorption equilibria and aided interpretation. The gases tested include pure methane (CH4), nitrogen (N2), and carbon dioxide (CO2), as well as binary mixtures of N2 and CO2 of different compositions. The coal pack was initially dry and free of gas, then saturated by each test gas at a series of increasing pore pressures at a constant effective stress until steady state was reached. Thus, the amount of adsorption varied, while the effective stress was held constant. Results show that, (i) permeability decreases with an increase of pore pressure at fixed injection-gas composition, and, (ii) permeability change is a function of the injected-gas composition. As the concentration of CO2 in the injection gas increases, the permeability of the coal decreases. Pure CO2 leads to the greatest permeability reduction among all the test gases. However, 10 to 20% by mole of N2 helps to preserve permeability significantly. According to the mixed-gas adsorption isotherms, adsorption and the selectivity of a particular gas species on coal surfaces is a function of pressure and the gas composition. Therefore, we conclude that loading coal surfaces with adsorbed gas at constant effective stress causes permeability reduction. Finally, gas adsorption and permeability of coal are correlated, simply to extend the usefulness of study results. Introduction Coalbed methane (CBM) has grown to supply approximately 10% of US natural-gas production and is becoming important worldwide as an energy source (EIA 2006). Conventional CBM-recovery procedures stimulate wells and produce CH4 by depressurizing the coalbed. A full understanding of the mechanisms underlying CBM production has yet to be established. Injection of CO2, N2, or mixtures of the two gases enhances CBM recovery significantly (Stevens et al. 1998; Stevens 2001). Coalbeds also present a potential sink for greenhouse gases (GHGs), such as CO2. One issue of particular interest for CO2 injection, and the subject of our study, is the sensitivity of coal permeability to the partial pressure of CO2 in the injection gas.
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Nguyen, Thi Hong Trang, Oriol Gutiérrez Sanchez, Vana Chinnappa Chinnabathini, Dimitra Papamichail, Deepak Pant, Didier Grandjean und Trang Nguyen. „Gas-Phase Pd Clusters-Modified Mesoporous Copper Oxide Hollow Spheres As Electrocatalysts for CO2 Reduction to Ethylene“. ECS Meeting Abstracts MA2023-02, Nr. 57 (22.12.2023): 2756. http://dx.doi.org/10.1149/ma2023-02572756mtgabs.
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Renewable energy-driven electrochemical CO2 conversion to value-added chemicals is a prospective strategy for addressing global carbon emission and energy consumption issues worldwide. Until today, only copper-based electrocatalysts can successfully transform CO2 into C2H4 or other desirable C2+ products, but their stability and product selectivity remain insufficient.1 Oxide-derived Cu mesoporous foam catalysts currently show the best selectivity toward C2+ product formation at particularly low overpotentials due to the availability of specific surface sites for C−C coupling in their structure and to the temporal trapping of gaseous intermediates inside the mesoporous catalyst material during CO2 electrolysis.2 To further improve their stability and product selectivity their surface can be modified with metallic clusters that can promote the adsorption of CO2 and the subsequent formation of intermediates. In particular, Pd clusters provide a favorable surface for the initial adsorption of CO2,3 while inducing a continuous restructuring of the Cu surface that maintains its catalytic properties for CO2 reduction to hydrocarbons.4 Herein, we report a novel highly efficient electrocatalyst for CO2 conversion in C2+ products based on mesoporous oxygen-rich copper hollow spheres prepared by a colloid templating method, whose surface is uniformly modified by the deposition of different loadings of well-defined Pd clusters of ca. 3 nm diameter using the laser ablation cluster beam deposition (CBD) technology.5 Primary electrochemical results show that these electrodes are able to reduce CO2 to ethylene with a faradaic efficiency of more than three times higher than that of commercial Cu2O nanoparticles under the same reaction conditions. A clear phase transition from CuO to Cu2O and metallic Cu is occurring under CO2 electro-reduction conditions as highlighted by XRD. These remarkable performances are likely originating from the facile gas charge transport via the mesoporous structure of the oxygen-rich copper spheres as imaged by SEM (Figure 1) as well as from their high surface area, which allows a high catalytic activity and a uniform accommodation of the metallic clusters. As CBD is a versatile technique that allows the deposition of virtually any type of well-defined cluster on a large variety of support, this work provides an attractive avenue to achieve stable selective multicarbon products via rational electrode design. References Kuhl KP, et al., Energy and Environmental Science, 2012;5 (5):7050-7059. Abhijit Dutta, et al., ACS Catal. 2016, 6, 3804−3814 Sichao Ma, et al., J. Am. Soc. 2017, 139, 47−50 Zhe Weng, et al., Angew. Int. Ed. 2017, 56, 13135 –13139 Chinnabathini V. C., et al., Nanoscale, 2023, DOI: 10.1039/D2NR07287D. Figure 1
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Nieszporek, Krzysztof. „Application of the Integral Equation Approach to the Study of Enthalpic Effects Accompanying Mixed-Gas Adsorption on Heterogeneous Solid Surfaces“. Adsorption Science & Technology 20, Nr. 3 (April 2002): 243–60. http://dx.doi.org/10.1260/026361702760254432.
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The possibilities of the Integral Equation approach for describing mixed-gas adsorption equilibria are presented. In this study, the energetic heterogeneity was described through the use of the Gaussian-like adsorption energy distribution function. As a result, very simple equations describing the isosteric heats of mixture components were obtained. The advantage of the model presented is the possibility of predicting the phase diagrams and enthalpic effects accompanying mixed-gas adsorption from a theoretical viewpoint based on pure-component adsorption data. New equations for isosteric heats of component mixtures were examined using the experimental data obtained by Dunne et al. (1996a, b, 1997), i.e. C2H6, CH4 adsorbed on silicalite and CO2, C2H6 adsorbed on NaX zeolite. The calculations are relatively simple and can be applied industrially.
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Hefti, Max, Lisa Joss, Zoran Bjelobrk und Marco Mazzotti. „On the potential of phase-change adsorbents for CO2 capture by temperature swing adsorption“. Faraday Discussions 192 (2016): 153–79. http://dx.doi.org/10.1039/c6fd00040a.
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We investigate the potential of a class of recently discovered metal–organic-framework materials for their use in temperature swing adsorption (TSA) processes for CO2 capture; the particularity of the considered materials is their reversible and temperature dependent step-shaped CO2 adsorption isotherm. Specifically, we present a comprehensive modeling study, where the performance of five different materials with step-shaped isotherms [McDonald et al., Nature, 2015, 519, 303] in a four step TSA cycle is assessed. The specific energy requirement of the TSA process operated with these materials is lower than for a commercial 13X zeolite, and a smaller temperature swing is required to reach similar levels of CO2 purity and recovery. The effect of a step in the adsorption isotherm is illustrated and discussed, and design criteria that lead to an optimal and robust operation of the considered TSA cycle are identified. The presented criteria could guide material scientists in designing novel materials whose step position is tailored to specific CO2 separation tasks.
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Sahu, Manoj Kumar, Uttam Kumar Sahu und Raj Kishore Patel. „Correction: Adsorption of safranin-O dye on CO2 neutralized activated red mud waste: process modelling, analysis and optimization using statistical design“. RSC Advances 6, Nr. 39 (2016): 32721. http://dx.doi.org/10.1039/c6ra90033j.
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Correction for ‘Adsorption of safranin-O dye on CO2 neutralized activated red mud waste: process modelling, analysis and optimization using statistical design’ by Manoj Kumar Sahu et al., RSC Adv., 2015, 5, 42294–42304.
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Yamaguchi, Akira, Hisanobu Taga und Masahiro Miyauchi. „(Invited) Investigation of Anion Role during Electrochemical CO2 Reduction on Copper Sulfide (CuS) by Potential-Step Method“. ECS Meeting Abstracts MA2024-02, Nr. 62 (22.11.2024): 4173. https://doi.org/10.1149/ma2024-02624173mtgabs.
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One of the candidate materials as CO2 reduction electrocatalysts is metal sulfide, generally because it possesses multiple adsorption sites to overcome scaling relationship. Furthermore, metal sulfide has unique redox property that not only metal sites but anion (sulfur) sites are redox active. To use this property efficiently, this work focused on potential-step method, in which two different electrode potential are applied to an electrode during CO2 reduction process. Previous electrochemical CO2 reduction works using metal copper (K. Kimura et al., ACS Catal., 10, 8632-8639, 2020) and tin sulfide (A. Woldu et al., Angew. Chem. Int. Ed., 62, 2023) electrodes as catalysts clearly demonstrated the usefulness of this method for CO2 reduction, however, its effect on anion behavior and CO2 reduction intermediate is under exploration. In this work, using copper sulfide (CuS) as a model compound, anion role on CO2 reduction reaction by potential-step method on metal sulfide was investigated. CuS was synthesized with solvothermal method using Cu(NO3)2, thioacetamide, and ethylene glycol as precursor solution. X-ray diffraction (XRD) and Raman measurements revealed that the obtained CuS possesses hexagonal structure. To prepare working electrode, dispersion solution of CuS in water and ethanol containing Sustainion as a binder was dropped onto carbon paper electrode. Electrochemical CO2 reduction properties were examined using H-type cell and 0.1 M KHCO3 aq. as an electrolyte. Platinum mesh and Ag/AgCl (sat. KCl) were used as counter and reference electrodes, respectively. By applying potential step method, selectivity for formic acid (HCOOH) was increased compared with conventional constant-potential method. XRD and X-ray photoelectron spectroscopy measurement revealed that Cu redox state was changed between Cu0 and Cu+ states during cathodic and anodic potential application, respectively. Furthermore, combining in situ Fourie Transformation Infrared spectroscopy and controlling experiment using Cu0 electrode, Cu2O, and Cu0 in the presence of S2- ion, this work proposed possible intermediate species and how they were affected by anions involved in the reaction to generate specific products. Namely, surface-adsorbed sulfur enhanced the adsorption of H+ ion and contributed to promoting all the reaction, while bulk sulfur stabilized CO intermediate to increase HCOOH selectivity. In addition, existence of oxygen generated Cu+ sites and resulting Cu+/Cu0 interface contributed to producing multi-carbon compounds. Our results indicated that the regulation of anion behavior by potential-step method is one of the promising strategies to control product selectivity of electrochemical CO2 reduction.
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Ramakrishnan Velmurugan, Adith, und Stefan Ringe. „Multiscale Modeling Reveals Mass Transport-Controlled Product Selectivity in Electrochemical CO2 Reduction on Cu“. ECS Meeting Abstracts MA2024-02, Nr. 61 (22.11.2024): 4096. https://doi.org/10.1149/ma2024-02614096mtgabs.
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Electrochemical CO2 reduction is one of the most promising processes for a sustainable closure of the artificial carbon cycle. A severe limitation for wide-scale industrial applicability has been the absence of an efficient and selective electrocatalyst for the reduction of CO2 to higher-reduced valuable chemicals and fuels. Cu is the only catalyst found to produce considerable amount of multicarbon products, albeit at high overpotentials. The mechanism of the conversion process is unclear, with different active sites and rate-determining steps being proposed. In addition, the mass transport of CO2 has been suggested to have a significant impact on the product selectivity1,2. Gas-diffusion-layer(GDL)-based electrolyzers have become a state-of-the-art solution to provide a high concentration of CO2 to the active sites to circumvent these mass transport limitations. In this work, we present a new multi-scale model based on first-principles kinetics3, and a modification of a recently reported gas diffusion electrode model4. We use this to generate a digital twin of experimental electrode systems and show that even in GDL systems, mass transport is the limiting factor governing all experimentally observed trends in product selectivity, irrespective of reaction mechanism or product pathway. We further find indications of C2 products being predominantly formed in wider, accessible pores, while C1 products are generated in deeper and thinner pores with less access to CO2. This work provides strong evidence for the importance of mass transport in designing CO2 electrolyzers. References: Watkins, N. B. et al. Hydrodynamics Change Tafel Slopes in Electrochemical CO2 Reduction on Copper. ACS Energy Lett. 8, 2185–2192 (2023). Ringe, S. et al. Double layer charging driven carbon dioxide adsorption limits the rate of electrochemical carbon dioxide reduction on Gold. Nat. Commun. 11, 33 (2020). Liu, X. et al. pH effects on the electrochemical reduction of CO(2) towards C2 products on stepped copper. Nat. Commun. 10, 1–10 (2019). Weng, L.-C., Bell, A. T. & Weber, A. Z. Modeling gas-diffusion electrodes for CO2 reduction. Phys. Chem. Chem. Phys. 20, 16973–16984 (2018).
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Cui, Xiaojun, und R. Marc Bustin. „Controls of Coal Fabric on Coalbed Gas Production and Compositional Shift in Both Field Production and Canister Desorption Test“. SPE Journal 11, Nr. 01 (01.03.2006): 111–19. http://dx.doi.org/10.2118/89035-pa.
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Summary The production rates of coalbed gas wells commonly vary significantly, even in the same field with similar reservoir permeability and gas content. The compositional variation in produced gas is also not every where predictable, although in most fields produced gas becomes progressively enriched in CO2 through the production life of a reservoir, such as parts of the San Juan basin. In contrast, it is generally observed that the ratio of CO2:CH4 declines with time during field and laboratory desorption testing of coal cores. In this study, we investigate numerically the importance of coal fabric, namely cleat spacing and aperture width, on the performance of coalbed gas wells and gas compositional shifts during production. Because of the cubic relationship between fracture permeability and fracture aperture width (and thus fracture porosity) for a given cleat permeability, the production profile of coal seams varies depending on whether the permeability is distributed among closely spaced fractures (cleat) with narrower apertures or more widely spaced fractures (cleat) with wider apertures. There is a lower fracture porosity for coal with widely spaced fractures than for coal with closely spaced fractures. Therefore, the relative permeability to gas increases more rapidly for coals with more widely spaced cleats as less dewatering from fractures is required, assuming that the fractures are initially water saturated. Increase in cleat spacing from 0.01 to 10 cm significantly enhances the peak gas production and shortens the period to reach peak production. The main stage of gas production is controlled by equilibrium desorption of gas from coals due to the relatively slow changes in reservoir pressure. The enrichment of CO2 in the production gas with time occurs because of the stronger adsorption of coals for CO2 than CH4. However, during desorption of coal cores, CO2 desorbs more rapidly than methane because desorption rate is governed more by diffusion than by sorption affinity, and CO2 has much higher effective diffusivity in microporous coals than CH4. Therefore, during canister desorption, there is a rapid increase in CO2 concentration in the desorbed gas followed by a steady decline in CO2 concentration, in contrast to the progressive enrichment of CO2 in produced gas from wells. Introduction Coalbed methane wells even within the same field invariably have dissimilar production rates, times to peak production, decline curves, and gas compositional shifts. Such variations in production and gas composition have been attributed to many factors in the literatures, including coal physical and chemical properties; variable damage caused by drilling, cementation, and inconsistent completion; and basin-scale geologic and hydrologic settings (Kaiser et al. 1994, Scott 2002, Cui et al. 2004a). Numerous studies (Remner et al. 1986, Reeves and Decker 1991, Reid et al. 1992, Young et al. 1992, Shi et al. 2002, Roadifer et al. 2003) have investigated the effects of coal properties and reservoir conditions on coalbed gas-well performance.
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Ma, Sheng Qian. „Gas Sensitivity of Cr Doped BN Sheets“. Applied Mechanics and Materials 799-800 (Oktober 2015): 166–70. http://dx.doi.org/10.4028/www.scientific.net/amm.799-800.166.
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Using Density Function Theory (DFT), the lattice parameters of Cr doped BN sheets are optimized, which are still kept on 2D planar geometry, and the band gap and the gas sensitivity are studied. The simulation results show that the gas molecule is very easy to be absorbed by Cr doped N in BN sheet, which is more stable structure. At the same time the band gap is very easy to be tuned by adsorption the gases on the Cr doped BN sheet. The band gap decreases from 4.704eV to 0.053eV. Through adsorption energy, we find Cr substitution N on BN sheet has strong sensitivity to the gases such as N2, O2, CO, NO, CO2, NO2, H2S, CH2O etc. In a word, Cr doped BN sheet is a promising material in gas sensors and tuning the band gap et al.
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Wu, Gang. „(Invited) Atomically Dispersed Metal Electrocatalysts for CO2 to CO Conversion: From Single to Dual Metal Sites“. ECS Meeting Abstracts MA2024-01, Nr. 37 (09.08.2024): 2163. http://dx.doi.org/10.1149/ma2024-01372163mtgabs.
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Carbon-supported nitrogen-coordinated single-metal site catalysts (i.e., M−N−C, M: Fe, Co, or Ni) are active for the electrochemical CO2 reduction reaction (CO2RR) to CO.(1) We comprehensively engineered FeN4 and NiNx sites for electrochemical CO2 reduction to CO considering the particle sizes of the catalysts, metal content, and the M−N (M: Fe or Ni) bond structures.(2, 3)The unique M-N-C model allows us to elucidate each factor′s role exclusively regarding the promotion of CO2 reduction.(4)Optimal particle sizes and Fe content provide favorable external factors to improve mass activity. Structural changes of M−N bonds controlled by thermal activation temperatures can intrinsically enhance CO selectivity and kinetic activity. Notably, the NiN3 active sites with optimal local structures formed at higher temperatures (e.g., 1200 °C) are intrinsically more active and CO-selective than NiN4, providing a new opportunity to design a highly active catalyst via populating NiN3 sites with increased density. Further improving their intrinsic activity and selectivity by tuning their N−M bond structures and coordination is limited. We further expand the coordination environments of M−N−C catalysts by designing dual-metal active sites.(5)The Ni-Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N-coordinated dual-metal site configurations are 2N-bridged (Fe-Ni)N6, in which FeN4 and NiN4 moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual-metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single-metal sites (FeN4 or NiN4) with improved intrinsic catalytic activity and selectivity. References Pan F, Zhang H, Liu K, Cullen D, More K, Wang M, et al. Unveiling Active Sites of CO2 Reduction on Nitrogen-Coordinated and Atomically Dispersed Iron and Cobalt Catalysts. ACS Catalysis. 2018;8(4):3116-22. Li Y, Adli NM, Shan W, Wang M, Zachman MJ, Hwang S, et al. Atomically dispersed single Ni site catalysts for high-efficiency CO2 electroreduction at industrial-level current densities. Energy & Environmental Science. 2022;15(5):2108-19. Mohd Adli N, Shan W, Hwang S, Samarakoon W, Karakalos S, Li Y, et al. Engineering Atomically Dispersed FeN4 Active Sites for CO2 Electroreduction. Angewandte Chemie International Edition. 2021;60(2):1022-32. Li J, Zhang H, Samarakoon W, Shan W, Cullen DA, Karakalos S, et al. Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction. Angewandte Chemie International Edition. 2019;58(52):18971-80. Li Y, Shan W, Zachman MJ, Wang M, Hwang S, Tabassum H, et al. Atomically Dispersed Dual-Metal Site Catalysts for Enhanced CO2 Reduction: Mechanistic Insight into Active Site Structures. Angewandte Chemie International Edition. 2022;61(28):e202205632.
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Kwon, Youngkook. „(Invited, Digital Presentation) Sub-Nanoscale Electrocatalyst Design for Enhanced CO2 Conversion“. ECS Meeting Abstracts MA2022-01, Nr. 36 (07.07.2022): 1617. http://dx.doi.org/10.1149/ma2022-01361617mtgabs.
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The majority of today’s research in electrochemical catalysis is centered in designing catalyst materials and processes that can surpass the current benchmarks of the classical catalysis. However, developments of the performance parameters of the important electrochemical reaction such as CO2 reduction reaction has been sluggish due to the intrinsic limitations such as adsorption energy scaling relations of the intermediate species.1 Recently, theoretical and experimental studies have revealed that the electrochemical reactions confined within a very small space with a wall separation under 1 nanometer outperforms the reactions without confinement.2-4 Theoretical models suggested that the enhancement from the nanoscopic confinement arises from the electronic interaction of the adsorbed species with multiple surfaces, which breaks the adsorption energy scaling relations of the important intermediate species.2 As a proof-of-concept, we synthesized novel copper oxide (CuOx) nanoparticles (NP) and tin oxide (SnOx) NP with highly controlled sub-nanoscale interplanar gaps of widths <1 nm via the lithium electrochemical tuning method. Transmission electron microscopy (TEM) and 3D tomo-scanning TEM (STEM) analysis confirm the presence of a distinct segmentation pattern and the newly engineered interparticle confined space in the designed catalysts. Atomic-gap controlled to 5-6 Å CuOx allows a current density exceeding that of unmodified CuOx nanoparticles by about 12 folds and a Faradaic efficiency of ≈80% to C2+.3 Separately, lithiated SnOx exhibits a significant increase in CO2RR vs. hydrogen evolution selectivity by a factor of ~5 with 20% higher formate selectivity relative to pristine SnO2 NPs at −1.2 VRHE.4 Density functional theory calculations indicate that the enhanced performance is attributable to a gap-stabilization of the rate-limiting *COOH and/or *OCHO intermediates. These results highlight the potential of controlled atomic spaces in directing electrochemical reaction selectivity and the design of highly optimized catalytic materials. Keywords : Electrocatalyst, CO2 reduction, Space Confinement, Sub-Nano Spacing Kwon et al., ACS Energy Lett., 2020, 5, 2987-2994. Lu and Cheng et al., J. Phys. Chem. Lett., 2020, 11, 1896-1902. Kwon et al., Adv. Energy Mater., 2020, 19034423. Kwon et al., Adv. Funct. Mater., 2021, 2107349.
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Hayase, Shunsuke, Asuka Morinaga, Qing Su, Hiroki Yoshimura, Ryansu Sai, Yasuyuki Kondo, Mamoru Ishikiriyama, Masaya Ibe, Yu Katayama und Yuki Yamada. „Experimental Insights into the Reaction Intermediates-Selectivity Relationship for Electrochemical CO2 Reduction Reaction“. ECS Meeting Abstracts MA2024-02, Nr. 67 (22.11.2024): 4732. https://doi.org/10.1149/ma2024-02674732mtgabs.
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Since the industrial revolution, the use of fossil fuels has increased CO2 concentration in the atmosphere, which has caused global warming to become a serious problem [1]. Thus, to realize a "carbon neutral" society, Electrochemical CO2 Reduction Reaction (CO2RR) has attracted attention. However, there are several challenges to the practical application of CO2RR, one of which is the improvement of product selectivity: the standard electrode potential of each reaction to various products is overlapped [2], and its large overpotential [3], making it difficult to selectively produce a specific product. In the pioneering study by Hori and co-workers, various metal electrodes were investigated and classified into four groups based on their primary reaction product: HCOO–-forming metals, CO-forming metals, hydrocarbon-forming metals, and CO2RR inactive metals (hydrogen-producing metals) [4]. Since the adsorption strength of the reaction intermediates has been considered the primary descriptor for the differences in reaction products, most studies have focused mainly on the adsorption energy. In recent years, more studies have focused on aspects other than the adsorption energies of O-bound and C-bound adsorbates to further improve product selectivity. Rossmeisl et al. suggest that the binding energy of H-bound adsorbates, in addition to O-bound and C-bound adsorbates, is an essential factor in explaining the final product [5]. Furthermore, the focus now expands to electrolyte properties, such as pH [ 6], cations [ 7], and anions [ 8] to control the stability of the reaction intermediates. As such, it is critical to experimentally probe the state of the reaction intermediates in situ to accurately understand the effect of the strategies mentioned above on the reaction pathway. In this study, we experimentally probe the reaction intermediates at various metal electrodes with different product selectivity using operando surface-enhanced infrared spectroscopy (SEIRAS). For the operando SEIRA measurements, we used a metal working electrode composed of a thin metal film electrodeposited on a Si prism coated with a Pt surface enhancement layer. Carbon rods were used as the counter electrode, Ag/AgCl as the reference electrode, and 1 M KHCO3 as the electrolyte. To compare the reactivity of reaction intermediates on different metal electrodes, we conducted linear sweep voltammetry (LSV) from 0.50 to –0.90 V vs RHE and probed the reaction intermediates during the potential sweep using SEIRAS. The result confirms the potential-dependent change in the reaction intermediates as well as the metal-dependent change in the composition of the reaction intermediates, suggesting successful observation of the CO2RR intermediates in different metal catalysts. Through this study, we attempted to interpret the correlation between the reactivity of each electrode and the properties of the reaction intermediates. Reference [1] Choi, S. et al, ChemSusChem 2009, 2, 796-854. [2] Jouny, M. et al, Ind. Eng. Chem. Res. 2018, 57, 2165–2177. [3] Yoo, J. S. et al, ChemSusChem 2016, 9, 358-363. [4] Hori, Y. et al, Modern Aspects of Electrochemistry 2008, 42, 89–189. [5] Bagger, A. et al, ChemPhysChem 2017, 18, 3266–3273. [6] Varela, A.S. et al, Catal. Today 2016, 260, 8-13. [7] Resasco, J. et al, J. Am. Chem. Soc. 2017, 139, 11277-11287. [8] Dunwell, M. et al, J. Am. Chem. Soc. 2017, 139, 3774-3783.
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Pagliari, Michele, Dario Montinaro, Emanuele Martelli, Stefano Campanari und Alessandro Donazzi. „Experimental Analysis of the Effect of Cathodic CO2 Supply to Industrial Solid Oxide Fuel Cells“. ECS Meeting Abstracts MA2023-01, Nr. 54 (28.08.2023): 105. http://dx.doi.org/10.1149/ma2023-0154105mtgabs.
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The integration of Solid Oxide Fuel Cells (SOFCs) in hybrid power generation systems offers the opportunity to achieve higher electric efficiencies. In the SOS-CO2 cycle [1], a newly developed cycle for blue power production (i.e., power generated starting from natural gas while capturing CO2), the SOFC cathode is supplied with mixtures of CO2 and O2, up to 79% CO2 molar fraction, while the anode is supplied with a reformate feed, containing H2, CH4, CO, CO2, and water vapour. Aim of this work is to experimentally evaluate the performance and the durability of industrial 5x5 cm2 Ni-YSZ anode-supported SOFCs under the SOS-CO2 cycle conditions, focusing on the effects of the CO2-rich cathodic atmosphere. The cells mounted a LSCF-based (La0.6Sr0.4Co0.2Fe0.8O3) single phase cathode, coated by a current collection layer of LSC (La0.6Sr0.4CoO3). Laboratory tests were performed at 700°C, acquiring polarization (I/V) curves and EIS spectra by means of a Horiba – FuelCon C50 Evaluator test station. Initial investigations with 7% humidified H2 and 21/79 O2/CO2 cathodic mixture revealed 25% power loss compared to the base case with cathodic air. The test showed not only that the loss of performance was stable in time, but also that the power reduction was reversible since the initial performance in air was recovered. The EIS spectra showed an increase of the polarization resistance and of the ohmic resistance upon feeding CO2. This latter observation suggested a reduction of the electronic conductivity of the cathode, compatible with the formation of Sr carbonates on the perovskite surface [2–4]. To assess the performance of the SOFC under the operating conditions of the SOS-CO2 cycle, the anode was supplied with reformate. Compared to the base case with humidified hydrogen and air, the current density at 0.7 V decreased by 37% (490 mA/cm2). When supplying the 21/79 O2/CO2 mixture at the cathode, the current density stabilized at 420 mA/cm2 (Figure 1). Durability tests (over 300 h) at 700°C with reformate and 21/79 O2/CO2 mixture highlighted a moderate decrease of the current density at 0.7 V. After these tests, the cathode was characterized post-mortem with XRD, SEM and Raman to analyse the consequences of the prolonged exposure to CO2. To further quantify the effect of CO2 on the cathode, symmetric button cells were also characterized with EIS, measuring ohmic and polarization resistances. The results suggested that the adsorption of CO2 is reversible and indicated a better suitability of LSCF- compared to LSC-based cathodes for operations with CO2-rich mixtures. Experiments performed between 550 and 700°C at varying CO2 and O2 partial pressures allowed to describe the kinetics of the oxygen reduction reaction and extract its activation energy. Overall, the results provided key elements for the integration of SOFCs in the SOS-CO2 blue power technology. References [1] R. Scaccabarozzi, M. Gatti, S. Campanari, and E. Martelli, “Solid oxide semi-closed CO2 cycle: A hybrid power cycle with 75% net efficiency and zero emissions,” Appl. Energy, vol. 290, no. February, p. 116711, 2021. [2] Y. Chen et al., “A highly active, CO2-tolerant electrode for the oxygen reduction reaction,” Energy Environ. Sci., vol. 11, no. 9, pp. 2458–2466, Sep. 2018. [3] Y. Yu et al., “Chemical characterization of surface precipitates in La0.7Sr0.3Co0.2Fe0.8O3-δ as cathode material for solid oxide fuel cells,” J. Power Sources, vol. 333, pp. 247–253, Nov. 2016. [4] J. Hwang et al., “CO2 Reactivity on Cobalt-Based Perovskites,” J. Phys. Chem. C, vol. 122, no. 35, pp. 20391–20401, 2018. Figure 1 - Polarization curves of 5x5 cm2 industrial SOFC supplied with 1.0 Nl/min of 7% humidified hydrogen and 2.5 Nl/min of air (black); 0.5 Nl/min of reformate mixture and 1.2 Nl/min of air (red); 0.5 Nl/min of reformate mixture and 1.2 Nl/min of cathodic 21% O2 / 79% CO2 mixture (green). Figure 1
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Kamiya, Kazuhide. „(Invited) High-Rate CO2 Reduction Reactions: From Electrocatalysts to Gas-Diffusion Electrodes“. ECS Meeting Abstracts MA2023-02, Nr. 47 (22.12.2023): 2366. http://dx.doi.org/10.1149/ma2023-02472366mtgabs.
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Excessive emissions of carbon dioxide (CO2) from the use of fossil fuels are becoming a serious obstacle to the sustainable development of society. Electrochemical CO2 reduction (CO2RR) into value-added products using solar electricity is a promising technology to close the carbon cycle and sequester anthropogenic CO2 into chemical feedstocks.[1] The practical implementation of CO2RR requires a high current density, as the current density for CO2RR is directly correlated to the capital cost of the electrodes and electrochemical cells. The use of gas diffusion electrodes (GDEs) effectively accelerates CO2RR by overcoming the mass transport limitation due to the inherently low diffusion and solubility of CO2 in water. This presentation summarises our recent studies on high-rate CO2RR from the point of view of both novel electrocatalyst designs and appropriate electrode assembly. Single-atom electrocatalysts (SAECs), consisting of single isolated metal sites dispersed on heterogeneous supports, are one of the promising electrocatalysts for high-rate gaseous CO2RR. We have employed various single metal-doped covalent triazine frameworks (M-CTFs) as a platform for CO2RR electrocatalysts on GDEs and systematically investigated them to derive sophisticated design principles using a combined computational and experimental approach.[2-4] The Ni-CTF exhibited both high selectivity and high reaction rate for CO production. In contrast, the Sn-CTF exhibited selective formic acid production, and the faradaic efficiencies (FEs) and partial current density reached 85% and 150 mA/cm2, respectively.[2] These results were in close agreement with the intermediate CO2RR adsorption strength obtained by DFT calculations. In addition to the synthesis of efficient electrocatalysts, the triple phase boundary (TPB) at the GDE, where the catalyst material, electrolyte, and gas pores intersect, needs to be enlarged for high-rate gaseous CO2RR.[5,6] We successfully increased the partial current density for multicarbon products (C2+) over cupric oxide (CuO) nanoparticles on gas diffusion electrodes in neutral electrolytes to a record value of 1.7 A/cm2 by maximizing the area of the CO2RR active interface.[5] In particular, we demonstrated that the thickness of catalyst layers was one highly sensitive factor in determining the maximum current density for C2+. Although the GDE and electrocatalyst used in this case are not unique, the optimized assembly elicits their undermined potential. [1] K. Kamiya, Nakanishi* et al. Chem. Lett. 2021, 50, 166-179. [2] S. Kato, K. Kamiya* et al. Chem. Sci., 2023, 14, 613–620. [3] P. Su, K. Kamiya*et al. , Chem. Sci., 2018, 9, 3941-3947. [4] K. Kamiya* Chem. Sci. 2020, 11, 8339–8349. [5] A. Inoue, K. Kamiya* et al. EES Catal. 2023, 1, 9-16. [6] T. Liu*, K. Kamiya* et al. Small 2022, 18, 2205323.
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Mogensen, Kristian. „Technology Focus: EOR Operations (June 2024)“. Journal of Petroleum Technology 76, Nr. 06 (01.06.2024): 78–79. http://dx.doi.org/10.2118/0624-0078-jpt.
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With 2024 marking the 75th anniversary of JPT, several articles published earlier this year in the magazine reflected on how our industry has evolved over the last 25 years thanks to technology breakthroughs and entrepreneurial mindsets. Some of the fields that came into production at the turn of the century are now potential candidates for enhanced oil recovery (EOR), and current oil price levels ought to make more EOR projects economically attractive. The EOR scene has evolved as well. Low-salinity waterflooding, originally thought to apply only in certain sandstone reservoirs, appears to be able to unlock additional reserves also for some carbonate formations, although the fundamental mechanisms are different. Within chemical EOR, we now have polymers and surfactants that can tolerate higher salinity and higher temperatures. Clear synergistic effects exist with low-salinity water, which can lower the required dosage of polymer and reduce adsorption in carbonates. Advancement in chemical formulations also can benefit mobility control in gasflooding applications through foam generation, with apparent synergistic effects when adding nanoparticles. There is no shortage of human ingenuity, and people are seeking inspiration from other industries such as biotech, nanotech, aerospace, and others. Yet, despite these advancements, many factors, such as suboptimal well placement, inadequate completion for inflow control, aging facilities, and the lower cost of infill drilling, can dampen the initial enthusiasm toward EOR. This is most certainly the case in an offshore environment where we have yet to see CO2 injection beyond the piloting phase. I remain optimistic that EOR has a role to play in maintaining the supply of hydrocarbons during the energy diversification era that we have just entered. Recommended additional reading at OnePetro: www.onepetro.org. SPE 214825 Using Natural Gas Liquid for EOR in a Huff‘N’Puff Process: A Feasibility Study by Amin Alinejad, University of Alberta, et al. SPE 216582 Alkali Polymer Flooding: Tackling Risks and Challenges From Feasibility Study to Pilot by A. Janczak, OMV, et al. IPTC 24484 Comprehensive Piloting Strategy To Derisk First CO2 EOR Development in Sultanate of Oman by Ramez Nasralla, Petroleum Development Oman OTC 34911 Pilot Tests of Steamflooding After Cyclic Steam‑N2‑CO2 Stimulation in Bohai Offshore With Large Well Spacing by Dong Liu, CNOOC, et al.
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Tsuda, Yuki, Kazuki Yoshii, Takao Gunji, Sahori Takeda und Nobuhiko Takeichi. „Electrodeposition of Cu with Amino Acids Toward Electrocatalytic Enhancement of CO₂ Reduction Reactions“. ECS Meeting Abstracts MA2024-02, Nr. 22 (22.11.2024): 1933. https://doi.org/10.1149/ma2024-02221933mtgabs.
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The electrochemical reduction of carbon dioxide (CO2) is attracting technology because it can convert CO2 into a useful resource with zero emissions by using surplus electricity and renewable energy. For achieving efficient electrolysis of CO2, the development of a high performance electrocatalysts is required. Copper (Cu) is the only metal that is capable of electrochemically converting CO2 to hydrocarbons, but the high overpotential of hydrocarbon formation and the low selectivity of the reduction products have been problems. One of the solutions to these problems is the hybridization of metal and organic materials, in which the metal serves as the CO2 reduction reaction sites and the organic material stabilizes the intermediates [1]. In this study, we have electrodeposited Cu with five different types of amino acids which is expecting stabilization of CO2 reductive intermediates and evaluated its catalytic activity of electrochemical reduction of CO2. The electrodeposited Cu with amino acids was obtained by a constant current electrolysis at -2.0 mA cm-2 for 1.0 C cm-2 from the aqueous solutions containing 10 mmol dm-3 CuSO4･5H2O, 0.1 mol dm-3 Na2SO4, and 1.0 mmol dm-3 amino acids in a three-electrode cell with carbon paper (CP) as the working electrode, platinum wire as the counter electrode, and Ag/AgCl as the reference electrode. The pH of electrolytic bath was fixed at 1.10 by adding H2SO4. The obtained electrodeposited Cu samples were characterized by Raman measurement, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy (EDS) measurement, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical reduction of CO2 has been conducted by a constant potential electrolysis at -1.27 V vs. RHE of 0.5 mol dm-3 KHCO3 aqueous solutions saturated with CO2. The amount of reductive gas products was quantified by gas chromatograph- mass spectrometer (GC-MS) and gas chromatograph thermal conductivity detector (GC-TCD). The chronopotentiograms obtained during the electrodeposition of Cu, both in the presence and absence of 1.0 mmol dm−3 of the various amino acids showed different potential required to reach a current of −4.0 mA depending on the amino acids. However, considering the result of the open-circuit-potential measurement, the amino acids do not form complexes with Cu2+, suggesting that the electrolysis species remain consistent regardless of the amino acid present in the Cu electrodeposition bath. Therefore, the differences observed in the chronopotentiograms during Cu electrodeposition are attributed to the adsorption of amino acids on the electrodeposited Cu. The adsorption of amino acids on electrodeposited Cu was confirmed by Raman spectra and EDS spectra obtained from cross-sectional HAADF-STEM images. The peak of Raman spectra originating from amino acids was observed from electrodeposited Cu when Cu electrodeposition was conducted with amino acids, confirming the higher ratio of N and Cu on the surface compared to within the particle in the EDS spectra. Surface morphologies were observed by using SEM. CP has fiber-like structure but electrodeposited Cu without and with amino acids were deposited such coating CP fiber. The particle size of electrodeposited Cu with amino acids was more homogeneous, and the particles were more densely packed together than pure electrodeposited Cu. However, changing diffraction patterns and peak broadening due to loading amino acids in XRD were not observed. The electrochemical reduction of CO2 on electrodeposited Cu samples was performed and the faradic efficiency (FE) of the CO2 reduction gas products were calculated. All electrodeposited Cu with and without amino acids showed a higher FE for the electrochemical reduction of CO2 to CH4 compared to Cu foil (24.2%) and different values depending on amino acids. In particular, electrodeposited with L-histidine containing imidazole groups showed a high FE of 67.6%, effectively suppressing the hydrogen evolution reaction. This finding highlights the important role of functional groups in amino acids, especially imidazole, in facilitating the electrochemical conversion of CO2 to CH4. This study shows that certain functional groups in amino acids have a crucial influence on the catalytic efficiency of electrodeposited Cu in CO2 reduction reaction applications. [1] S. Jia et al., Angew. Chem. Int. Ed. 2021, 60, 10977–10982.
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Pontrefract, R. D., C. W. Ng, E. E. Ashton und G. Bergeron. „The use of thick sections with transmission electron microscopy in combination with scanning electron microscopy to study the attachment of Neisseria gonorrhoeae to vero cells infected with Chlamydia trachomatis“. Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 78–79. http://dx.doi.org/10.1017/s042482010010247x.
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Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) are well known pathogens associated with sexually transmitted disease. Clinical studies have shown that these organisms are frequently found together, and it has been suggested that gonorrhoeae be used as a marker for chlamydial infections. The reason for the high rates of co-infection is not known. However, in vitro studies (Ng et al. manuscript in preparation) have shown that the adsorption of NG to Vero cells pre-infected with CT is increased at least twenty times compared with that obtained with non-infected cells. In order to determine the areas of attachment and the fine structure of the attachment sites of the gonococci to the CT infected Vero cells, both transmission electron microscopy (TEM) using thick (0.25-0.5μm) sections and scanning electron microscopy (SEM) were used.To prepare samples for TEM, Vero (African green monkey kidney) cells were grown in T-flasks for 48h in M199 + 10% fetal calf serum at 37C in an atmosphere containing 5% CO2.
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Qiao, Yu, Brian Seger, Degenhart Hochfilzer, Bjørt Óladóttir Joensen, Wanyu Deng und Ib Chorkendorff. „(Digital Presentation) Investigations on the Ethanol/Ethylene Bifurcation and Restructure of Cu/Ag Catalysts for Electrochemical CO2 Reduction“. ECS Meeting Abstracts MA2022-01, Nr. 36 (07.07.2022): 1614. http://dx.doi.org/10.1149/ma2022-01361614mtgabs.
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Electrochemical CO2 reduction (ECO2R) converts greenhouse gas CO2 into valuable fuels and chemicals, and thus helps with closing the anthropogenic carbon cycle. Currently, Cu is the only known material being capable of producing a variety of hydrocarbons and alcohols, while the poor selectivity limits its further use. Ethanol and ethylene have been proved to go through similar pathways but their bifurcation is yet to be fully understood. It has been found that introducing Ag atoms into Cu lattice could shift the product distribution toward ethanol compared to ethylene. However, previous studies have proposed contradictory speculations: DFT calculations predict the introduced Ag atoms prefer to dope on the undercoordinated sites on Cu surface [1], while experiments have proved that C-C coupling occurs at these sites and is promoted when they are occupied by Ag [1]–[3]. Literature also interpreted various mechanisms of the interaction between Cu and, such as the constrained effect [1], [4], “spillover” [5], and different C-C coupling pathways between *CO and *CHx (x=1,2) at the boundaries [6]. The oxidation state [7] and faceting [1] as well as the composition of CuAg catalysts over time have been observed during the reaction course, but explicitly real-time information remains scarce. To provide more mechanistic information on the above controversies, we prepared both bimetallic (with miscible Cu and Ag phases s) and surface alloy (with separated Cu and Ag phases) CuAg thin films by physical vapor deposition (PVD) and galvanic exchange, respectively. Ex situ X-ray Photoelectron Spectroscopy (XPS) and O perando X-ray Absorption Spectroscopy (XAS), including X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) on surface alloy CuAg are performed under ECOR/ECO2R conditions to investigate the oxidation state and coordination numbers of Cu and Ag. By this means, electron transfer and the interface miscibility between Cu and Ag are identified. Combined with DFT calculations, we speculated possible doping sites of Ag atoms in the Cu lattice and potential adsorption sites of the produced intermediates for ethanol/ethylene formation. Besides, variations of the oxidation state, electric and geometric local structure, as well as the transformation in crystallinity of the CuAg catalysts over time are monitored by correlating XAS with operando Grazing Incidence X-ray Diffraction (GIXRD). The produced CO intermediates are substantiated to be the reason for Cu-enrichment occurring on the CuAg electrodes as speculated. References: [1] D. Higgins et al., “Guiding Electrochemical Carbon Dioxide Reduction toward Carbonyls Using Copper Silver Thin Films with Interphase Miscibility,” ACS Energy Lett., vol. 3, no. 12, pp. 2947–2955, 2018, doi: 10.1021/acsenergylett.8b01736. [2] L. Wang et al., “Selective reduction of CO to acetaldehyde with CuAg electrocatalysts,” Proc. Natl. Acad. Sci. U. S. A., vol. 117, no. 23, pp. 12572–12575, 2020, doi: 10.1073/pnas.1821683117. [3] C. Hahn et al., “Engineering Cu surfaces for the electrocatalytic conversion of CO2: Controlling selectivity toward oxygenates and hydrocarbons,” Proc. Natl. Acad. Sci. U. S. A., vol. 114, no. 23, pp. 5918–5923, 2017, doi: 10.1073/pnas.1618935114. [4] E. L. Clark, C. Hahn, T. F. Jaramillo, and A. T. Bell, “Electrochemical CO2 Reduction over Compressively Strained CuAg Surface Alloys with Enhanced Multi-Carbon Oxygenate Selectivity,” J. Am. Chem. Soc., vol. 139, no. 44, pp. 15848–15857, 2017, doi: 10.1021/jacs.7b08607. [5] S. Lee, G. Park, and J. Lee, “Importance of Ag-Cu Biphasic Boundaries for Selective Electrochemical Reduction of CO2 to Ethanol,” ACS Catal., vol. 7, no. 12, pp. 8594–8604, 2017, doi: 10.1021/acscatal.7b02822. [6] Y. C. Li et al., “Binding Site Diversity Promotes CO2 Electroreduction to Ethanol,” J. Am. Chem. Soc., vol. 141, no. 21, pp. 8584–8591, 2019, doi: 10.1021/jacs.9b02945. [7] S. B. Scott et al., “Absence of Oxidized Phases in Cu under CO Reduction Conditions,” ACS Energy Lett., vol. 4, no. 3, pp. 803–804, 2019, doi: 10.1021/acsenergylett.9b00172.
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Qian, Yuhang, und Dongge Ma. „Covalent Organic Frameworks: New Materials Platform for Photocatalytic Degradation of Aqueous Pollutants“. Materials 14, Nr. 19 (27.09.2021): 5600. http://dx.doi.org/10.3390/ma14195600.
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Covalent organic frameworks (COFs) are highly porous and crystalline polymeric materials, constructed by covalent bonds and extending in two or threedimensions. After the discovery of the first COF materials in 2005 by Yaghi et al., COFs have experienced exciting progress and exhibitedtheirpromising potential applications invarious fields, such as gas adsorption and separation, energy storage, optoelectronics, sensing and catalysis. Because of their tunablestructures, abundant, regular and customizable pores in addition to large specific surface area, COFs can harvest ultraviolet, visible and near-infrared photons, adsorb a large amount of substrates in internal structures and initiate surface redox reactions to act as effective organic photocatalysts for water splitting, CO2 reduction, organic transformations and pollutant degradation. In this review, we will discuss COF photocatalysts for the degradation of aqueous pollutants. The state-of-the-art paragon examples in this research area will be discussed according to the different structural type of COF photocatalysts. The degradation mechanism will be emphasized. Furthermore, the future development direction, challenges required to be overcome and the perspective in this field will be summarized in the conclusion.
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Li, Jialang, Manila Ozhukil Valappil, Erwan Bertin und Viola Ingrid Birss. „N-Doped Nanoporous Carbon Scaffolds As Catalysts for CO2 Reduction“. ECS Meeting Abstracts MA2022-01, Nr. 39 (07.07.2022): 1782. http://dx.doi.org/10.1149/ma2022-01391782mtgabs.
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The need for clean energy solutions in order to significantly lower our carbon footprint is placing increasing attention on renewable energy, such as wind and solar. However, these technologies suffer from intermittency issues, thus making efficient energy storage and conversion a major requirement. One of the solutions to this problem is electrochemical CO2 reduction (CO2RR), using renewable energy to produce green fuels and chemicals. However, the reduction of CO2 is thermodynamically and kinetically unfavorable. To overcome this, the development of highly efficient and selective electrocatalysts is a key goal of CO2RR research. Carbon has been attracting interest as a promising candidate due to its high specific surface area, good conductivity, and low-cost. However, its catalytic performance is limited by the electroneutrality of the carbon atoms in the primarily graphitic lattice. In order to activate the CO2 molecules and enhance the adsorption of intermediates, a range of novel carbon catalysts has been developed, with nitrogen doping being the most common approach. The N atom has a similar size as C and thus the lattice mismatch after doping is minimal [1]. At the same time, the N atom also has a higher electronegativity than C which will break the electroneutrality of the carbon lattice and enhance the conductivity of the material [2-3]. Furthermore, N doping results in a range of N-based surface species, thus potentially allowing the tuning of the CO2RR products [4]. In this work, a novel, self-supported, nanoporous carbon scaffold (NCS) was used as the carbon substrate. The NCS is a templated, binder-free mesoporous carbon material with tunable pore sizes, a high surface area, good conductivity, and scalability [5]. Here, N doping of the NCS was achieved by heat treatment in NH3. An in house flow cell that can be switched between flow-through and flow-by modes was developed, allowing the NCS to be used as a model material to understand the impact of fluid flow on mass transfer limitations in the CO2RR and on any local pH effects that may be present. The CO2RR performance was tested in the flow cell using a CO2-saturated KHCO3 solution. The bare NCS was confirmed to generated only H2, while the N-doped NCS gives roughly a 50:50 ratio of H2:CO at all potentials, with the onset potential being ca. -0.55 V vs RHE. The effect of the NCS pore size was also investigated, showing that an NCS membrane with a nominal 85 nm pore diameter produced roughly 45% CO, while the NCS-12 (12 nm pore size) material gave somewhat more CO (ca. 55-60%). At the same time, the NCS-12 gave lower current densities, despite its higher surface area, likely due to poorer pore accessibility. Furthermore, running the cell in the flow-through mode gave higher currents at all of the NCS-based catalysts, most likely due to removal of trapped gases. Current work is focused on determining the effect of the N content and the type of N-based functionalities attached to the NCS surface on the CO2RR performance. References [1] Ji, Yan, et al. “Plasma-regulated N-doped carbon nanotube arrays for efficient electrosynthesis of syngas with a wide CO/H2 ratio.” Science China Materials 63.11 (2020): 2351-2357. [2] Liu, Weiqi, et al. “Utilizing spatial confinement effect of N atoms in micropores of coal-based metal-free material for efficiently electrochemical reduction of carbon dioxide.” Applied Catalysis B: Environmental 272 (2020): 118974. [3] Gao, Kun, et al. "Efficient metal‐free electrocatalysts from N‐doped carbon nanomaterials: mono‐doping and co‐doping." Advanced Materials 31.13 (2019): 1805121. [4] Duan, Xiaochuan, et al. "Metal‐free carbon materials for CO2 electrochemical reduction." Advanced Materials 29.41 (2017): 1701784. [5] Atwa, Marwa, et al. "Scalable nanoporous carbon films allow line-of-sight 3D atomic layer deposition of Pt: towards a new generation catalyst layer for PEM fuel cells." Materials Horizons 8.9 (2021): 2451-2462.
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Oezaslan, Mehtap, Sonja Blaseio, Abhijit Dutta, Motiar Rahaman, Kiran Kiran, Peter Broekmann und Björn Mahrt. „Understanding the Transition Process of Cu Oxide to Metallic Under the CO2 Reduction Conditions Probed By Operando Quick-XAS“. ECS Meeting Abstracts MA2022-02, Nr. 49 (09.10.2022): 1900. http://dx.doi.org/10.1149/ma2022-02491900mtgabs.
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During the last decades, significant efforts have been made to directly convert CO2 as a potential feedstock into hydrocarbons as fuels and/or basic chemicals for industrial applications. The electrochemical CO2 reduction reaction (CO2RR) is a promising alternative for a large-scale production of hydrocarbons. However, there are still some challenges including poor product selectivity and highly complex multiple-step reaction mechanisms.[1] In order to convert CO2 on a Cu electrode, high overpotentials up to 1.0 V are required, which make the energy efficiency still rather poor and lead to competition with the H2 evolution.[2] Additionally, the morphology of the Cu materials i.e. structure and ‘chemical state’ (metallic vs oxidized, high vs low coordinated) strongly influence the performance of the CO2RR. Recently, we have shown the critical potential of oxide-metal transition processes for Cu oxide foam annealed at 300°C probed by operando XAS, XRD and Raman spectroscopy.[3,4] All three operando techniques showed an entire reduction of Cu oxide to metallic before the production of hydrocarbons starts. [3,4] In this work, we have investigated the kinetics of both electrochemical oxide-metal reduction and CO2RR on nanoporous Cu foams as catalyst precursor annealed at four different temperatures (100°C, 200°C, 300°C, 450°C) in air using operando Quick X-ray Adsorption Spectroscopy (Quick-XAS). The Quick-XAS measurements were carried out in a custom-made spectro-electrochemical flow cell using 0.5 M KHCO3 as the electrolyte, while the XAS-Spectra were measured in transmission mode. The Quick-XANES data was analyzed by linear combination fit (LCF) and principle component analysis (PCA) to monitor the potential dependent changes of the chemical state and coordination number of the Cu species. Based on the Cu K-edge XANES and EXAFS data, we show that the annealing temperature strongly influences the chemical state of the Cu species. More precisely, the population of the Cu(II) species within the as prepared foams increases with increasing annealing temperature. Starting from the different ratios of Cu(0):Cu(I): Cu(II), the oxide-metal transition processes are shifted in the cathodic direction by applying potential steps of 100 mV. With an increase in annealing temperature, this oxide-metal transition is more rapid and occurs at lower cathodic overpotentials, but still before the production of hydrocarbons begins. In contrast, the potential jump experiments of several hundreds of mV lead to different kinetics of the oxide-metal reduction of Cu species. These transition processes and the resulting structure of porous Cu foams have a huge impact on the product distribution for CO2RR. Altogether, our results provide deeper insights into the oxide-metal transition processes to form the catalytically active Cu species for hydrocarbon formation during CO2RR. Reference: [1] S. Nitopi et al., Chemical Reviews, 2019, 119, 7610. [2] C. W. Li et al., Journal of the American Chemical Society, 2012, 134, 7231. [3] A. Dutta et al., Chimia, 2021, 75, 733. [4] A. Dutta et al., Journal of Catalysis, 2020, 389, 592.
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Novoselova, Inessa, Sergiy Kuleshov und Anatoliy Omel'chuk. „(Digital Presentation) Electrochemical Conversion of CO2 into Tungsten Carbides in Molten Salts“. ECS Meeting Abstracts MA2023-01, Nr. 26 (28.08.2023): 1744. http://dx.doi.org/10.1149/ma2023-01261744mtgabs.
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Huge amounts of anthropogenic emissions of the greenhouse gas carbon dioxide into the Earth's atmosphere are one of the key factors causing global warming. To mitigate the consequences of the severe climate changes caused by this phenomenon, over the last two decades great efforts of researchers have been directed towards the development of sustainable, environmentally friendly, carbon neutral and, if possible, not very expensive (in terms of used energy and inexpensive consumables) technologies for capture, conversion and storage (CCS) of CO2. Electrochemical conversion of CO2 using molten salts can rightfully be classified as CCS technology. In this case, carbon dioxide from various sources of its generation (fossil fuel power plants, industrial enterprises with a high carbon footprint) can be captured by molten salt (as a result of its physical dissolution, or chemical absorption by molten salt), and then electrochemically be converted into high value-added carbon-containing compounds: (a) carbon monoxide [1]; (b) carbon allotropes of various structures and modifications [2]; (c) refractory metal carbides [3], and various composites based on them. The reaction path and composition of the cathode products will depend on the electrolysis conditions. Elemental carbon synthesis precursor can be – carbon dioxide, directly dissolved in the molten salt mixture (direct reduction of CO2), as well as the carbonate anion, formed as a result of carbon dioxide interaction with oxide ions which are presented in the electrolyte bath (indirect reduction of CO2). This work presents the result of research concerning the electrochemical synthesis of the powders of tungsten carbides (WC and W2C) in chloride melt NaCl-KCl (1:1) under carbon dioxide pressure at the temperature range 700 – 800 оС. Refractory metal precursors are its oxy-anions (WО3; W2O7 2-; Меn x[WO4]nx-2; WO3F3 3- where Me – Na; K; Li; Mg; Ca; n – valance of metal Me). The formation of the new forms of tungsten electrochemical active particles in electrolyte is realized by the changing (control) of acidity of the melt. Carbon source is CO2, which was introduced into the electrolyzer under the excessive pressure of 0.1 – 1.7 MPa. The creation of excessive gas pressure is necessary condition for the increasing of the rate of electrolytic process (current densities) throw the rise of CO2 solubility in chloride melt. The general scheme of the high-temperature synthesis of tungsten carbides by the method of Molten Salt Carbon Electrochemical Transformation (MS-CCT) is presented in Fig. 1. The electrochemical investigations of partial and joint electroreduction of tungsten carbide precursors were carried out by the method of cyclic voltammetry. The areas of potentials and current densities, where the joint electrochemical discharge of tungsten carbide precursors (a narrow range of deposition potentials) occurs up to refractory metal and carbon takes place were found. Electrolytical synthesis of nano-sized (10 – 30 nm) powders of tungsten carbides (WC, W2C) and composites WC-C (up to 5 wt % of free carbon); W2C-WC; WC-C-Pt was carried out from the melts of different chemical composition; and the characterization of obtained products was fulfilled by the methods of chemical analysis, X-ray diffraction, DTG, BET adsorption, scanning and transmission electron microscopy. Synthesized composite materials based on tungsten carbides of various compositions were investigated as a cathode material in the reaction of electrolytic splitting of water for hydrogen production in a sulfuric acid solution [4]. The obtained results showed that the best activity has a composite of tungsten monocarbide WC with a content of free carbon up to 5 wt.%. The hydrogen onset potential for this electrode is -0.02 V, the overvoltage of hydrogen release at ik = 10 mA/cm2 is -110 mV, the exchange current is 7.0×10-4 A/cm2, the Tafel slope – -85 mV/dec. The presence of free carbon on the surface of tungsten carbides electrode improves its catalytic activity, increasing the area of the active surface. The catalytic activity of electrodes made of tungsten monocarbide increases with the introduction of platinum (up to 10 wt %) into the composite. References Kaplan V, Wachtel E, Gartsman K et al (2010) Conversion of CO2 to CO by electrolysis of molten lithium carbonate. J Electrochem Soc 157:B552–B556. Novoselova I.A., Kushkhov Kh.B., Malyshev V.V., Shapoval V.I. (2001) Theoretical foundations and implementation of high-temperature electrochemical synthesis of tungsten carbides in ionic melts. Theor. Found. Chem. Eng. 35:175–187. Novoselova I.A., Kuleshov S.V., Volkov S.V. et al (2016) Electrochemical synthesis, morphological and structural characteristics of carbon nanomaterials produced in molten salts. Electrochim Acta 211:343–355. Novoselova I, Kuleshov S, Fedoryshena E et al (2018) Electrochemical synthesis of tungsten carbide in molten salts, its properties and applications. ECS Trans 86:81–94. Figure 1
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Robertson, Eric P., und Richard L. Christiansen. „Modeling Laboratory Permeability in Coal Using Sorption-Induced Strain Data“. SPE Reservoir Evaluation & Engineering 10, Nr. 03 (01.06.2007): 260–69. http://dx.doi.org/10.2118/97068-pa.
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Summary Sorption-induced strain and permeability were measured as a function of pore pressure using subbituminous coal from the Powder River basin of Wyoming, USA, and high-volatile bituminous coal from the Uinta-Piceance basin of Utah, USA. We found that for these coal samples, cleat compressibility was not constant, but variable. Calculated variable cleat-compressibility constants were found to correlate well with previously published data for other coals. Sorption-induced matrix strain (shrinkage/swelling) was measured on unconstrained samples for different gases: carbon dioxide (CO2), methane (CH4), and nitrogen (N2). During permeability tests, sorption-induced matrix shrinkage was demonstrated clearly by higher-permeability values at lower pore pressures while holding overburden pressure constant; this effect was more pronounced when gases with higher adsorption isotherms such as CO2 were used. Measured permeability data were modeled using three different permeability models that take into account sorption-induced matrix strain. We found that when the measured strain data were applied, all three models matched the measured permeability results poorly. However, by applying an experimentally derived expression to the strain data that accounts for the constraining stress of overburden pressure, pore pressure, coal type, and gas type, two of the models were greatly improved. Introduction Coal seams have the capacity to adsorb large amounts of gases because of their typically large internal surface area (30 to 300 m2/g) (Berkowitz 1985). Some gases, such as CO2, have a higher affinity for the coal surfaces than others, such as N2. Knowledge of how the adsorption or desorption of gases affects coal permeability is important not only to operations involving the production of natural gas from coalbeds but also to the design and operation of projects to sequester greenhouse gases in coalbeds (RECOPOL Workshop 2005). As reservoir pressure is lowered, gas molecules are desorbed from the matrix and travel to the cleat (natural-fracture) system, where they are conveyed to producing wells. Fluid movement in coal is controlled by diffusion in the coal matrix and described by Darcy flow in the fracture (cleat) system. Because diffusion of gases through the matrix is a much slower process than Darcy flow through the fracture (cleat) system, coal seams are treated as fractured reservoirs with respect to fluid flow. However, coalbeds are more complex than other fractured reservoirs because of their ability to adsorb (or desorb) large quantities of gas. Adsorption of gases by the internal surfaces of coal causes the coal matrix to swell, and desorption of gases causes the coal matrix to shrink. The swelling or shrinkage of coal as gas is adsorbed or desorbed is referred to as sorption-induced strain. Sorption-induced strain of the coal matrix causes a change in the width of the cleats or fractures that must be accounted for when modeling permeability changes in the system. A number of permeability-change models (Gray 1987; Sawyer et al. 1990; Seidle and Huitt 1995; Palmer and Mansoori 1998; Pekot and Reeves 2003; Shi and Durucan 2003) for coal have been proposed that attempt to account for the effect of sorption-induced strain. Accurate measurement of sorption-induced strain becomes important when modeling the effect of gas sorption on coal permeability. For this work, laboratory measurements of sorption-induced strain were made for two different coals and three gases. Permeability measurements also were made using the same coals and gases under different pressure and stress regimes. The objective of this current work is to present these data and to model the laboratory-generated permeability data using a number of permeability-change models that have been described by other researchers. This work should be of value to those who model coalbed-methane fields with reservoir simulators because these results could be incorporated into those reservoir models to improve their accuracy.
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Winzely, Maximilian, Adam Hugh Clark, Piyush Chauhan, Paul Maurice Leidinger, Meriem Fikry, Tym de Wild und Thomas J. Schmidt. „Monitoring the Activation of a Aucu Aerogel Catalyst for Electrochemical CO2 Reduction via in Situ XAS“. ECS Meeting Abstracts MA2024-02, Nr. 62 (22.11.2024): 4240. https://doi.org/10.1149/ma2024-02624240mtgabs.
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To drive the further development of electrochemical CO2 reduction technologies, there is an urgent need for highly active catalysts that minimize unwanted side reactions and that also possess a large specific surface area. While nanostructured catalysts typically fulfill the latter requirement, they often use porous carbon supports that improve the nanoparticles’ dispersion but can shift the product selectivity towards undesirable H2 formation.[1] This challenge could be solved by using unsupported aerogels consisting of interconnected nanodomain networks of highly porous materials such as nano-wires or -particles, which provide a large surface area while minimizing unwanted side reactions.[2] So far, precious metals such as gold (Au) and silver (Ag) have shown remarkable activity and selectivity as CO2-reduction catalysts for CO production.[3] However, due to the high cost of such noble metals, improving their mass-specific activity is essential. One strategy to attain this, especially for Au, is to reduce the adsorption energy of the catalyst’s surface towards CO by changing the electronic structure of the d-band through alloying with other metals. In this context, ordered AuCu structures have proven to be promising candidates for improving the CO2-to-CO activity and selectivity.[4] With the motivation to combine both of the above approaches (i.e., Au-alloying with Cu and the absence of a C-support), in this study we present an AuCu aerogel with an average domain size of ≈ 7 nm that exhibits an exceptionally high faradaic efficiency of 87 % for CO at -0.6 V versus the reversible hydrogen electrode (RHE). This corresponds to a ≈ 2-fold higher Au-mass-specific partial current density for CO when compared to an equivalent, monometallic Au aerogel. Notably, this enhanced activity and selectivity are achieved by performing a potential cycling procedure prior to the CO2 reduction potential hold that involves cyclic voltammetry (CV) between 0.1 and 1.7 V vs. RHE at a scan rate of 50 mV/s until a stable voltammogram is achieved. To investigate the changes in the electronic and structural properties which have happened to the catalyst during this potential cycling, we performed an in situ grazing incidence X-ray absorption spectroscopy (XAS) measurements in the course of these CVs. Chiefly, these spectroelectrochemcial tests were carried out in the same cell used for the assessment of the CO2 reduction performance, ensuring for the first time that the mass-transport conditions encountered by the catalyst during these XAS measurements are identical to those in the CO2-reduction activity and selectivity tests. Figure 1 illustrates the changes observed throughout the potential cycling procedure in the Cu K- and Au L3-absorption edges, whereby the acquired spectra were submitted to a multivariate curve resolution (MCR) analysis. For the Cu K spectra, a total of three components were identified to describe the whole dataset, and it becomes evident that as the number of cycles increases, the copper oxide phase (component 1 in Figs. 1b and 1c) diminishes while a metallic phase (component 2, identified as an AuCu alloy through EXAFS fitting) becomes more prominent. In the case of the Au L3 data, only two components were discerned to describe the dataset, and both of them were identified as distinct AuCu alloy phases through EXAFS fitting. With an increasing number of cycles, component 2 (featuring a higher oxide content than component 1) becomes dominant at positive potentials, suggesting an increasing Au content on the aerogel’s surface as the potential cycling procedure progresses. In summary, in this contribution we present an AuCu aerogel catalyst exhibiting a high activity and selectivity for CO production that is achieved by cyclic voltammetry treatment prior to holding CO2 reduction potential. The results derived from the in situ XAS measurements on this material indicate that this process effectively removes the copper oxide domains initially present in the catalyst, forming a novel AuCu alloy phase while simultaneously enriching the aerogel’s surface with Au. References Baturina, O.A., et al., CO2 Electroreduction to Hydrocarbons on Carbon-Supported Cu Nanoparticles. ACS Catalysis, 2014. 4(10): p. 3682-3695. Cai, B. and A. Eychmuller, Promoting Electrocatalysis upon Aerogels. Adv Mater, 2019. 31(31): p. e1804881. Hori, Y.M., A.; Kikuchi, K.; Suzuki, S, Electrochemical Reduction of Carbon Dioxides to Carbon Monoxide at a Gold Electrode in Aqueous Potassium Hydrogen Carbonate. J. Chem. Soc., Chem. Commun., 1987. 10: p. 728-729. Liu, K., et al., Electronic Effects Determine the Selectivity of Planar Au-Cu Bimetallic Thin Films for Electrochemical CO(2) Reduction. ACS Appl Mater Interfaces, 2019. 11(18): p. 16546-16555. Figure 1
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Jung, Hyeonjung, Md Delowar Hossain und Michal Bajdich. „Impact of Local Structure and Spin on the ORR Performance of Single Atom M-N-C Catalysts“. ECS Meeting Abstracts MA2024-02, Nr. 11 (22.11.2024): 1461. https://doi.org/10.1149/ma2024-02111461mtgabs.
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Transition metal single-atom catalysts supported on N-doped graphene (M-N-Cs) offer significant advantages in metal utilization and uniformity of active sites compared to traditional heterogeneous catalysts. They are particularly notable for their superior electrocatalytic Oxygen Reduction Reaction (ORR) performance. Various modifications have been explored, including different metal combinations, different first shell elements (N, C, S, B), and coordination numbers, to enhance electrocatalytic ORR activities. Another emerging focus is the link between their local structure and spin state. The Zhenan Bao and Jaramillo groups recently found that the catalytic activity of the NiNx moiety stems from its tetrahedrally distorted structure because it stabilizes the high-spin Ni state more than the low-spin state.[1] The local structure and its distortion can be modified by adjusting the carbon nanotube diameter,[2] pore size,[3] layering,[4] or by adding ligands at the first or second shell.[5] In this study, we have conducted a computational screening of M-N-Cs with 3d, 4d, and 5d metals and local structures including square planar, tetragonal pyramidal, and tetrahedral symmetries. Metals in their divalent states within the MN4 units exhibited a V-shaped trend in formation energy correlated with increasing atomic numbers across each series. This pattern appears to be linked to the interaction between the two electrons of the N4 ligand and the d electron count of the metals, and it also emerged in the *O/*OH adsorption energy plots. Additionally, the preferred spin state varied with the metal type and structural symmetry, influencing electron distribution and crystal field splitting. These factors collectively impacted the binding energies with adsorbents, subsequently altering oxygen reduction reaction (ORR) activity. Further, we explored the adsorption energies of various intermediates (*CO, *H, *Cl, and *N2H) relevant to carbon dioxide reduction reaction (CO2RR), hydrogen evolution reaction (HER), chlorine evolution reaction (ClER), and nitrogen reduction reaction (NRR), respectively. Our primary objective was to identify optimal metal-structure combinations for enhanced catalytic performance. To achieve this, we considered several descriptors including partial Integrated Crystal Orbital Hamilton Population (ICOHP), metal d-band center, Madelung energy, and metal ionization potential. Moving forward, we aim to extend these findings by incorporating distorted coordination environments and integrating experimental synthesis strategies to induce such distortions, potentially unlocking new pathways for catalytic efficiency enhancement. [1] Koshy, David M., et al. "Investigation of the Structure of Atomically Dispersed NiNx Sites in Ni and N-Doped Carbon Electrocatalysts by 61Ni Mössbauer Spectroscopy and Simulations." Journal of the American Chemical Society 144.47 (2022): 21741-21750. [2] Cepitis, Ritums, et al. "Surface curvature effect on dual-atom site oxygen electrocatalysis." ACS Energy Letters 8.3 (2023): 1330-1335. [3] Glibin, Vassili P., et al. "Non-PGM electrocatalysts for PEM fuel cells: thermodynamic stability and DFT evaluation of fluorinated FeN4-based ORR catalysts." Journal of The Electrochemical Society 166.7 (2019): F3277. [4] Wu, Yahui, et al. "Boosting CO2 electroreduction over a cadmium single‐atom catalyst by tuning of the axial coordination structure." Angewandte Chemie International Edition 60.38 (2021): 20803-20810. [5] Choi, Daeeun, et al. "Bridging the Catalytic Turnover Gap Between Single‐Atom Iron Nanozymes and Natural Enzymes by Engineering the First and Second Shell Coordination." Advanced Materials (2023): 2306602.
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Nagamori, Kiyotaka, Satoshi Aoki, Mayumi Ikegawa, Yasuhiro Seki, Hiroshi Igarashi, Kayoko Tamoto und Makoto Uchida. „The Effect of Pt Catalysts with Controlled Hydrophilicity on the Surface on the Dispersibility of Ionomers and Durability in Polymer Electrolyte Fuel Cells“. ECS Meeting Abstracts MA2024-02, Nr. 50 (22.11.2024): 4951. https://doi.org/10.1149/ma2024-02504951mtgabs.
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Polymer electrolyte fuel cells (PEFCs) are attracting attention as a promising system that can generate electricity without emitting greenhouse gases such as CO2. In recent years, there has been growing interest in the use of FCVs for Heavy duty commercial vehicles(HDV) due to the relationship between cruising range, vehicle size, and fuel costs, and many manufacturers are actively pursuing development. HDV require high power density and a cruising range of over 1 million km on a single charge, and achieving this requires a large amount of platinum catalyst, so striking a balance between performance and durability is important1. The distribution of ionomers on the surface of the catalyst and within the catalyst layer is an important topic for improving performance, and has been clarified through extensive research, including the mechanism of activity reduction due to adsorption poisoning of Pt by sulfonic acid functional groups2,3 and the adsorption and occupation of Pt by ionomers deposited in the pores or on the outer surface of the support4,5. In order to discuss the dispersion of the ionomer on the catalyst surface, it is necessary to consider the balance of the surface conditions of the platinum and carbon support surface. We evaluated the effect of differences in hydrophilicity on the dispersion of ionomers by chemical treatment of the catalyst surface to give differences in hydrophilicity derived from the balance of functional groups and Pt oxides. Furthermore, assuming use under actual operating conditions, the impact of the hydrophilicity of the catalyst on durability was evaluated using water-generating load cycle durability test6. We prepared a reference catalyst of 50% Pt/Ketjen EC300J (K-1), and then prepared K-2 and K-3 with different hydrophilicities using two different surface treatment methods. K-2 was found to have excessive hydrophilicity, while K-3 had moderate hydrophilicity. Through surface treatment, we found that there were differences in the amount of hydrophilic functional groups and the amount of Pt oxide. In addition, we observed the dispersibility of the ionomers using a low-accelerate-voltage TEM, and found differences in the dispersibility of the ionomer layer on the catalyst surface and the pore blockage within the catalyst layer depending on the hydrophilicity. We achieved high dispersibility of the ionomers by appropriately controlling the hydrophilicity, as in K-3. In addition, the Pt utilization ratio (U Pt) was measured using electrochemical measurements. K-3showed a high U Pt with moderate hydrophilicity. In addition, in water-generating load cycle durability test, K-3 with moderate hydrophilicity showed high durability. Based on this, it is expected that the surface condition of the catalyst can be appropriately controlled to promote improvements in the MEA structure, its performance, and durability. s durability. Acknowledgement This work was partially based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References 1)D. A. Cullen, et al., Nat. Energy, 6, 462−474(2021). 2)K. Kodama, et al., ECS Trans., 58, 363−368(2013). 3)K. Kodama, et al., ACS Catal., 8 , 694−700(2018). 4)Y. C. Park, et al., J. Power Sources, 315, 179−191(2016). 5)A. Kobayashi, et al., ACS Appl. Energy Mater., 4, 2307−2317(2021). 6)C. Takei, et al., J. Power Sources, 324, 729−737(2016). Figure 1
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Rai, Sandhya, Vishal Metri, Christopher D. Taylor und Nicholas J. Laycock. „The Effects of Trace H2S Levels on the Structure of Surface Scales in CO2 Corrosion“. ECS Meeting Abstracts MA2023-02, Nr. 11 (22.12.2023): 1068. http://dx.doi.org/10.1149/ma2023-02111068mtgabs.
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The CO2 corrosion of carbon steel is very strongly influenced by the formation of surface scales of corrosion products. Hence, the structure and composition of those scales has been the subject of much research. For oxygen-free brines in contact with gaseous CO2 at partial pressures up to ~50 bar, and temperatures up to ~120 °C, the formed scales are generally found to consist of a mixture of Fe3C (cementite) and FeCO3 (siderite). In simulated oil and gas production brines, the siderite incorporates Ca and Mg, while DeMarco et al [1] identified the scales that form over short times at ambient temperature as a mixture of Fe2(OH2)CO3 and Fe2O2CO3. Williams and colleagues [2-7] carried out detailed studies of the scales formed in solutions of moderate chloride content (0.5 – 1 M), saturated with CO2 at ~ 1 bar, pH adjusted to ~ 6.5 and at temperatures of ~ 80 °C. For the solutions containing only sodium chloride, siderite (FeCO3) was the major phase in the scale, though chukanovite (Fe2(OH)2CO3) was also present in some cases. With the addition of magnesium chloride, both siderite and chukanovite were always found in the scale, while there was no evidence of magnesium incorporation until the bulk concentration of MgCl2 was ~ 0.1 M. Considering the effect of low-level Cr and Mo alloying, it was found in the base sodium chloride solutions that mixed siderite/chukanovite scales were formed, but the scale became thinner and the chukanovite-to-siderite ratio decreased with alloy content. Even for alloys with 3.5 wt% Cr there was no evidence of discrete Cr (hydr)oxide layers within the scale. However, the addition of trace levels of H2S (∼ 0.5 μM) produced more significant changes. First, only chukanovite and FeS (mackinawite) were now found in the scale, with no siderite. Second, for the unalloyed steel and for alloys with 1 wt% Cr and up to 0.7% Mo, the scales were highly porous. Finally, for the 3.5wt% Cr alloy, a non-porous, protective layer was formed, about 200–600 nm thick. In this paper, we utilize ab-initio techniques to investigate the effects of very low level H2S on carbonate scale formation. In the past DFT has been used to understand the various aspects of corrosion and the design of corrosion inhibitors for various conditions [9-11]. We have used similar approach for studying the H2S adsorption on siderite and chukanovite surfaces, considering the experimental observation by Hassan et al [2], that trace amounts of H2S result in chukanovite over siderite. Initial studies show that there is a 0.7 eV higher interaction energy (more thermodynamically favorable) for H2S adsorption on chukanovite compared to siderite. This may imply the possibility that H2S could encourage chukanovite formation over siderite formation in aqueous environments.We further investigate this possibility using DFT to understand the mechanism that leads to formation of chukanovite. We aim to use implicit solvation in order to bring the effect of water in the vicinity. We further use the cluster approach within DFT, to explain the effect that alloying has on the scale formation. We take a bare Fe cluster and replace one of its atoms with an alloying element and study the electronic structure in the presence of H2S and CO2. The potential energy surface gets modified for a H2S—Fe interaction in the presence of Ni. We expect that this work would help us to have a deeper understanding of how alloying can impact or rather initiate certain kind of scale formation over others. References: De Marco, Z.T. Jiang, B. Pejcic and E. Poinen, J. Electrochem. Soc. 152 (2005) B389. Hassan Sk, J. Qi, N. Al-Qahtani, A. M. Abdullah, N. Laycock, M. P. Ryan, and D. E.Williams, J. Electrochem. Soc., 166, C3233 (2019). Hassan Sk, A.M. Abdullah, M. Ko, B. Ingham, J. Qi, N. Laycock, M.P. Ryan and D.E. Williams, J. Electrochem. Soc., 165, C278-C288 (2018). Ko, B. Ingham, N. Laycock and D.E. Williams, Corrosion Science, 90, 192-201 (2015). Ko, B. Ingham, N. Laycock, and D.E. Williams, Corrosion Science, 80, 237–246 (2014). Ko, N.J. Laycock, B. Ingham and D.E. Williams, Corrosion, 68, 1085-1093 (2012). Ingham, M. Ko, N. Laycock, J. Burnell, P. Kappen, J. A. Kimpton and D. E. Williams, Corrosion Science, 56, 96-104 (2012). Ingham, M. Ko, G. Kear, P. Kappen, N. Laycock, J. A. Kimpton and D. E. Williams, Corrosion Science, 52, 3052-3061 (2010). Anton Kokalj, Corrosion Science, 196, 109939 (2022). Li, S., Frankel, G. S., & Taylor, C. D. (2022). Journal of The Electrochemical Society, 169(8), 081506. Ke, H., & Taylor, C. D. (2019). Corrosion, 75(7), 708-726. Figure 1
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Qin, Xueping, Tejs Vegge und Heine Anton Hansen. „Cation-Coordinated Inner-Sphere CO2 Electroreduction at Au-Water Interfaces“. ECS Meeting Abstracts MA2023-01, Nr. 50 (28.08.2023): 2582. http://dx.doi.org/10.1149/ma2023-01502582mtgabs.
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The electrocatalytic CO2 reduction reaction (CO2RR) is a promising technology to store renewable energy and mitigate the increase of CO2 concentration.1-2 Understanding the electrode-electrolyte interfacial reaction mechanism from the atomic level is instrumental for both catalyst design and catalytic system’s optimization. Electrolyte ions are critical for CO2RR and the competitive hydrogen evolution reaction (HER), however, the role of alkali metal cations is highly controversial. For example, a recent study by Koper and co-workers highlighted the role of alkali metal ion coordination,3 whereas another work by Hu et al. ascribed the cation effect to the modulation of local electric field.4 In order to explore the crucial cation role in electrocatalytic reactions, electrode-electrolyte interfacial models should be properly constructed by including explicit water solvents and alkali metal cations. In our previous work, CO2 activation step at Au-water-2K interfaces has been studied by ab initio molecular dynamics (AIMD) simulations with the kinetic barrier of 0.61 eV.5 To determine the rate-determining step (RDS) during CO2RR on Au surfaces, the full reaction pathway involving the subsequent electron and proton transfer steps is further investigated, and the reaction kinetics is evaluated by the slow-growth sampling approach integrated with AIMD simulations (SG-AIMD). As shown in Figure 1, the complete free energy diagram of CO2RR under electrochemical conditions is constructed for the first time, where the transition state (TS) structures are shown on top. It is illustrated that such a cation-coordinated inner-sphere CO2RR at Au-water interfaces is facile, and the first electron transfer with the concomitant adsorption during CO2 activation is the RDS. Furthermore, HER pathway is also explored, which is highly suppressed by local alkali cations showing much higher kinetic barrier in the rate-limiting Volmer step. Our systematic atomic-scale study via ab initio molecular dynamics simulations demonstrates that CO2RR shows superior catalytic activity under the cation promotion effect which is originated from the short-range coordination interaction between reaction intermediates and cations. This study motivates the development of periodic models mimicking the electrode-electrolyte interface under electrochemical conditions, which can be extended into studying various electrocatalytic reactions via AIMD simulations. References (1) Nitopi, S.; Bertheussen, E.; Scott, S. B.; Liu, X.; Engstfeld, A. K.; Horch, S.; Seger, B.; Stephens, I. E. L.; Chan, K.; Hahn, C.; Nørskov, J. K.; Jaramillo, T. F.; Chorkendorff, I., Chem. Rev. 2019, 119, 7610-7672. (2) Seh, Z. W.; Kibsgaard, J.; Dickens, C. F.; Chorkendorff, I.; Nørskov, J. K.; Jaramillo, T. F., Science 2017, 355, eaad4998. (3) Monteiro, M. C., Dattila, F., Hagedoorn, B., García-Muelas, R., López, N. and Koper, M., Nat. Catal., 2021, 4, 654-662. (4) Gu, J., Liu, S., Ni, W., Ren, W., Haussener, S. and Hu, X., Nat. Catal., 2022, 5, 268-276. (5) Qin, X.; Vegge, T.; Hansen, H. A., J. Chem. Phys. 2021, 155, 134703. Figure 1. Complete free energy landscape of CO2RR at Au-water interfaces with two K cations. The structures of transition state (TS) are shown on top. The charges transferred to key intermediates (*CO2, *COOH, *CO) are shown in the insert figure, where the charge transfer in CHE model is indicated by dashed lines. Color code: Au, golden; K, purple; C, blue; O, red; H, white. Figure 1
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AIB, Ekejiuba. „Universal “Plug and Play” Real-Time Entire Automotive Exhaust Effluents, Industry Vents and Flue Gas Emissions Liquefiers: The Game Changer Approach-Phase Two Category“. Petroleum & Petrochemical Engineering Journal 7, Nr. 2 (04.04.2023): 1–56. http://dx.doi.org/10.23880/ppej-16000349.
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The first in the series of Azuberths Game Changer publications “Synergy of the Conventional Crude Oil and the FT-GTL Processes for Sustainable Synfuels Production: The Game Changer Approach-Phase One Category” a.k.a. (DOI: 10.23880/ppej16000330) is targeted at reducing 80 per cent CO2 emissions from the internal combustion engines by upgrading from the conventional crude oil refinery products to the synthetic fuels products (ultra-low-carbon fuels). This paper will focus on the complete elimination of the remaining 20 per cent CO2 emissions (i.e. to achieve zero- CO2 emissions) in transportation and power generating internal combustion engines as well as in the other centralized emissions/emitters such as petroleum industry flare lines, industrial process and big technology industries scrubber flue gas, et cetera. This invention stems from similar biblical quote {Isaiah 6:8-New International Version (NIV)} which states, and then I heard the voice of the Lord saying, “Whom shall I send? And who will go for us?” And I (Isaiah) said, “Here am I. Send me!” Laterally, in this case I (Azunna) said, “Here am I. Please use me”. Hence the aftermath, IJN-Universal Emissions Liquefiers is a plug and play units for all categories of pollutants discharge into the atmosphere. The work is motivated by the scientific facts that (i) The release of CO2 from automotive exhaust effluents, industry vents and flue gas emissions into the atmosphere contributes to greenhouse gas (GHG) accumulation causing global warming hence climate changes issues such as flooding of coastlines/sea-rising, melting of the glaciers, disrupted weather patterns, bushburning/wildfire, depletion of Ozone layer, smog and air pollution, acidification of water bodies, runaway greenhouse effect, etc. (ii) Every gas stream (e.g., flue gas) can be made liquid by e.g. a series of compression, cooling and expansion steps and once in liquid form, the components of the gas can be separated in a distillation column. (iii) Captured liquefied gases can be put to various uses, especially carbon dioxide (CO2 ), which can be used for the production of renewable energy via Synfuels such as the e-fuel/solar fuel. The natural atmosphere is composed of 78% nitrogen, 21% oxygen, 0.9% argon, and only about 0.1% natural greenhouse gases, which include carbon dioxide, organic chemicals called chlorofluorocarbons (CFCs), methane, nitrous oxide, ozone, and many others. Although a small amount, these greenhouse gases make a big difference - they are the gases that allow the greenhouse effect to exist by trapping in some heat that would otherwise escape to space. Carbon dioxide, although not the most potent of the greenhouse gases, is the most important because of the huge volumes emitted into the air by combustion of fossil fuels (e.g., gasoline, diesel, fuel oil, coal, natural gas). In general, the major contributors to the greenhouse effect are: Burning of fossil fuels in automobiles, deforestation, farming processing and manufacturing factories, industrial waste and landfills, increasing animal and human respiration, etc. The increased number of factories, automobiles, and population increases the amount of these gases in the atmosphere. The greenhouse gases never let the radiations to escape from the earth atmosphere and increase the surface temperature of the earth. This then leads to global warming. The petroleum industry well sites vent/flare gases (methane, ethane, propane, butanes, H2 O (g), O2 , N2 , etc.). Internal combustion engines (automobiles-cars, vehicles, ships, trains, planes, etc.) release exhaust effluents (containing H2 O (g), CO2 , O2 , and N2 ); steam generators in large power plants and the process furnaces in large refineries, petrochemical and chemical plants, and incinerators burn considerable amounts of fossil fuels and therefore emit large amounts of flue gas to the ambient atmosphere. In general, Flue gas is the gas exiting to the atmosphere via a “flue”, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. The emitted flue gas contains carbon dioxide CO2 , carbon monoxide CO, sulphur oxide SO2 , nitrous oxide NO and particulates. Furthermore, GTL plants produce CO2 , H2 O and waste heat, while both pyrolysis and gasification plant generate gaseous products consisting of (a mixture of non-condensable gases such as H2 , CO2 , and CO and light hydrocarbons “e.g. CH4 ” at room temperature, as well as H2 O (g), O2 and complex hydrocarbons e.g. C2 H2 , C2 H4 , etc.). In general, all combustion is as a result of air-fuel mixture burning (i.e. air or oxygen mixing directly with biomass/ coal or with liquid/gaseous hydrocarbon inside internal combustion engines), releases carbon dioxide and steam (H2 O) back into the atmosphere as well as producing energy for work. Specifically, during combustion, carbon combines with oxygen to produce carbon dioxide (CO2 ). The principal emission from transportation and power generating internal combustion engines is carbon dioxide (CO2 ). The level of CO2 emission is linked to the amount of fuel consumed and the type of fuel used as well as the individual engine’s operating characteristics. For instance, diesel-powered engines have higher emission than petrol/gasoline-powered engines. Although emphasis is places more on CO2 , this investigation is ultimately concerned with the real-time liquefaction of all the components of gaseous release/emissions -related to air pollution/health problem. It is believed that the mortality rate from air pollution is eight times larger than the mortality caused by car accidents each year. Pollutants with the strongest evidence for public health concern include particulate matter (PM), ozone (O3 ), nitrogen dioxide (NO2 ) and sulphur dioxide (SO2 ). All the exhaust effluents gases/flue gas and vent/flare gases are captured by liquefying them and then put to various uses, to achieve “Net zero” emissions. Fundamentally, the objective of the present invention is to develop a compact device (Universal Emissions Liquefiers) that can be retro-fitted onto the exhaust tailpipe-end of the internal combustion engines (diesel-powered, gasoline-powered, and hybrid automobiles-cars, vehicles, SUV’s, trucks, motor cycles, tri-cycles, portable electric generators, sea and cargo ships/ boats, trains, planes, rockets, etc.) and outlet of industrial machines that release flue gases through exhaust/scrubber channels, as well as crude oil, refined products storage tanks that vent greenhouse gases into the atmosphere, coal processing units/ plants and turn them into liquid { CO2 (l), N2 (l), O2 (l), etc.} or powdered components or chemically transform them in realtime with selective catalysts to any other specific compound, e.g. treating CO2 with hydrogen gas (H2) can produce methanol (CH3 OH), methane (CH4 ), or formic acid (HCOOH), while reaction of CO2 with alkali (e.g. NaOH) can give carbonates (NaHCO3 ) and bicarbonates (Na2 CO3 ). Nitrogen (N2 ) to ammonia (NH3 ) or Hydrazine (N2 H4 ), and molecular oxygen (O2 ) to hydrogen peroxide (H2 O2 ), et cetera. Alternatively, in new automobiles designs, the universal emissions liquefiers’ device can be directly net-worked on the floor alongside the catalytic converters and may eliminate the need for muffler/silencer/resonator. This is achieved by the application of any of the five main gas capture/separation technologies: Liquid absorption, Solid adsorption, Membrane separation (with and without solvent- organic or inorganic), Cryogenic refrigeration/distillation, and Electrochemical pH-swing separation or their combination to selectively trap and liquefy the individual pollutants. According to the fact from CarBuster, almost 0.009 metric tons of carbon dioxide is produced from every gallon of gasoline burned, which means that the average car user makes about 11.7 tons of carbon dioxide each year from their cars alone
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Akbari, Masoud, Chiara Crivello, Octavio Graniel, Martial Defort, Skandar Basrour, Kevin Musselman und David Muñoz-Rojas. „ZIF-Based Metal-Organic Frameworks for Cantilever Gas Sensors“. ECS Meeting Abstracts MA2022-01, Nr. 52 (07.07.2022): 2144. http://dx.doi.org/10.1149/ma2022-01522144mtgabs.
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Among the different gas sensing platforms, cantilever-based sensors have attracted considerable interest in recent years thanks to their ultra-sensitivity and high-speed response. The gas sensing mechanism in a dynamic cantilever sensor is based on its resonance frequency shift upon adsorption of a gas molecule on the sensor. In order to sensitize the surface of a cantilever, a sensitive receptor material with large surface area is required. Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials composed of metal ions coordinated to organic linkers. MOFs are promising for gas sensing applications as they have large surface area, rich porosity with adjustable pore size and excellent selective adsorption capability for various gasses.[1] Zeolite imidazole frameworks (ZIFs) are a class of MOFs where metals with tetrahedral coordination (i.e. Zn, Co, Fe, Cu) are the central node and the ligands are imidazolate-based organic molecules. In this work, we developed a ZIF-based thin film for dynamic cantilever gas-sensing applications. We employed a novel atmospheric pressure spatial atomic layer deposition (AP-SALD)[2][3] technique to deposit a ZnO sacrificial layer on the silicon cantilevers. This technique allows the deposition of high-quality films at atmospheric pressure, faster than conventional ALD. The ZnO layer was then converted to a particular ZIF film with desired porosity and size, through a MOF-CVD process.[4] A gas-sensing bench setup was developed for the cantilever actuation and read-out. We present the chemical and morphological properties of the ZIF, as well as the frequency response of the sensor to various gases. The device showed reliable sensitivity to humidity, CO2 and several VOCs. References [1] X. F. Wang, X. Z. Song, K. M. Sun, L. Cheng, and W. Ma, “MOFs-derived porous nanomaterials for gas sensing,” Polyhedron, vol. 152, pp. 155–163, 2018. [2] D. Muñoz-Rojas, T. Maindron, A. Esteve, F. Piallat, J. C. S. Kools, and J. M. Decams, “Speeding up the unique assets of atomic layer deposition,” Mater. Today Chem., vol. 12, pp. 96–120, 2019. [3] K. P. Musselman, C. F. Uzoma, and M. S. Miller, “Nanomanufacturing: High-Throughput, Cost-Effective Deposition of Atomic Scale Thin Films via Atmospheric Pressure Spatial Atomic Layer Deposition,” Chem. Mater., vol. 28, no. 23, pp. 8443–8452, 2016. [4] I. Stassen et al., “Chemical vapour deposition of zeolitic imidazolate framework thin films,” Nat. Mater., vol. 15, no. 3, pp. 304–310, 2016.
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Markunas, Brianna, und Joshua David Snyder. „Phenol-Mediated Proton Shuttling Enables Electrochemical Hydrogenation of Phenol in Alkaline Electrolytes on Rhodium“. ECS Meeting Abstracts MA2024-02, Nr. 53 (22.11.2024): 3613. https://doi.org/10.1149/ma2024-02533613mtgabs.
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Thermal chemical hydrogenation (TCH) is a key reaction for upgrading petroleum and biomass feedstocks to value- added fuels and chemicals. TCH requires high operating temperatures and pressures which results in high energy consumption and CO2 emissions. Electrochemical hydrogenation (ECH) is a mild alternative where applied potential drives the hydrogenation of hydrocarbons with protons from the aqueous electrolyte near ambient conditions. Phenol is a simple representative compound for renewable lignocellulosic feedstocks that has been the focus of recent ECH studies. The added complexity from the electrolyte and applied potential in aqueous ECH systems requires a fundamental understanding of these reaction parameters on ECH activity in-order to overcome current limitations, including faradaic efficiency losses to the competitive hydrogen evolution reaction (HER). Furthermore, the wide range of reaction conditions employed in the phenol ECH literature makes comparison of the ECH performance difficult. Phenol ECH on PGMs is commonly performed in electrolytes in a pH range of 1-5, assuming that the ECH of phenol follows a Langmuir Hinshelwood (LH) mechanism [1, 2]. One study reported a 95% faradaic efficiency (FE) for phenol ECH on rhodium at pH 10 [3], but no further investigation into the source of this promising activity at alkaline pH has been conducted. In this work we study the role of electrolyte pH on phenol ECH on platinum and rhodium. We show that there are differing pH trends for ECH activity between platinum and rhodium, with the highest ECH rates on platinum at pH 1 and the highest rates on rhodium at pH 9, near the pka of phenol. We show using cyclic voltammetry and in-situ electrochemical FTIR that this pH dependent behavior results from the interplay between hydrogen adsorption kinetics, differences in phenol/hydrogen coverage on each metal, and competition with HER. We show that the electrolyte pH dictates the balance between a hydrogen atom transfer (LH) mechanism and a phenol-mediated proton coupled electron transfer mechanism. With this insight, we show that the unique properties of rhodium and the acid-base chemistry of phenol and the electrolyte buffer can be leveraged for higher ECH rates and FE. [1] Singh, N., et al., Aqueous Phase Catalytic and Electrocatalytic Hydrogenation of Phenol and Benzaldehyde over Platinum Group Metals. Journal of Catalysis 2020, 382, 372–384. https://doi.org/10.1016/j.jcat.2019.12.034. [2] Song, Y., et al., Integrated Catalytic and Electrocatalytic Conversion of Substituted Phenols and Diaryl Ethers. Journal of Catalysis 2016, 344, 263–272. https://doi.org/10.1016/j.jcat.2016.09.030. [3] Song, Y., et al., Aqueous Phase Electrocatalysis and Thermal Catalysis for the Hydrogenation of Phenol at Mild Conditions. Applied Catalysis B: Environmental 2016, 182, 236–246. https://doi.org/10.1016/j.apcatb.2015.09.027.
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Van Daele, Kevin, Nick Daems, Deepak Pant und Tom Breugelmans. „An in-Depth Exploration of the Electrocatalytic Stability of Sn-Based Electrocatalysts for the Electrochemical CO2 Reduction Towards Formate“. ECS Meeting Abstracts MA2023-02, Nr. 58 (22.12.2023): 2798. http://dx.doi.org/10.1149/ma2023-02582798mtgabs.
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Over the past decades, the electrochemical CO2 reduction (eCO2R) into industrially valuable products has become one of the most promising technologies to valorize anthropogenic CO2 emission, while also providing a means of energy storage for intermittent renewable sources. A wide variety of products, such as formic acid/formate (HCOOH/HCOO-), carbon monoxide (CO), methane (CH4), methanol (CH3OH), ethylene (C2H4) etc., can be obtained. The eCO2R towards formic acid/formate (FA), a 2-electron transfer process, has the potential to generate the highest revenue per mole of consumed electrons, which originates from the fact that FA can be produced with high Faradaic efficiencies on cheap and earth abundant metals, such as Sn, Bi, Pb, Hg, In and Cd. State-of-the-art Sn-based electrocatalysts have been reported to reach selectivities approaching 100% at industrially relevant current densities. Looking at the long-term performance of these state-of-the-art Sn-based electrocatalysts, only seven have a minimum reported stability of 72 hours, with the maximum being 100 days (2400 h) of stable operation. Even though Bi-based catalysts currently outperform Sn-based electrocatalysts in terms of stability, Sn-based catalysts are still believed to be viable alternatives if an extended stability of over 80 000 hours can be achieved. Sn-based electrocatalyst stability thus remains inadequate and appears to be a crucial piece to the puzzle. 1 In this research, we elucidate the major degradation pathways that impair long-term electrocatalytic performance, by determining the chemical and physical phenomena that occur during the electrochemical reduction reaction on the surface and in the bulk of Sn-based catalysts. Simultaneously, the possibilities of a variety of mitigation strategies are explored, and insight into stability issues related to Sn-based electrocatalysts and CO2 electrolysers is gathered. Firstly, Sn was incorporated into a more open, carbon based supporting material (N-doped ordered mesoporous carbon) in an attempt to significantly increase the stability by inhibiting agglomeration and nanoparticle detachment. An N-doped carbon supporting material was chosen for its high surface area and in order to enhance the initial adsorption of CO2, which is commonly referred to as the rate-limiting step, for the eCO2R towards formate, in literature. These novel electrocatalysts provide us with valuable insights into the influence of the supporting material on their electrochemical performance and highlighted the potential of the particle confinement strategy to increase the morphological electrocatalyst stability during electrolysis. In a next step, we demonstrated the successful application of the recently developed pomegranate-structured SnO2 (Pom. SnO2) and SnO2@C (Pom. SnO2@C) nanocomposite electrocatalysts for the efficient electrochemical conversion of CO2 to formate. With an initial selectivity of 83 and 86% towards formate and an operating potential of -0.72 V and -0.64 V vs. RHE, respectively, these pomegranate SnO2 electrocatalysts are able to compete with most of the current state-of-the-art Sn-based electrocatalysts in terms of activity and selectivity. Given the importance of electrocatalyst stability, long-term experiments (24 h) were performed and a temporary loss in selectivity was noticed for the Pom. SnO2@C electrocatalyst. Ex situ XRD and XPS were used to link this temporary selectivity loss of the Pom. SnO2@C electrocatalyst to the in situ SnO2 reduction to metallic Sn. While this electrochemical degradation occurs in both electrocatalysts, it is more pronounced in the Pom. SnO2@C electrocatalyst since it isn’t offset by the morphological electrocatalyst degradation revealing new and selective SnOx active sites, as suspected for the Pom. SnO2. Furthermore, we were able to largely restore its selectivity upon drying and exposure to air. Of all the used (24 h) electrocatalysts, the pomegranate SnO2@C had the highest selectivity over a time period of one hour, reaching an average recovered FE of 85%, while the commercial SnO2 and bare pomegranate SnO2 electrocatalysts reached an average of 79 and 80% FE towards formate, respectively. Finally, the pomegranate structure of Pom. SnO2@C was largely preserved due to the presence of the heterogeneous carbon shell, which acts as a protective layer, physically inhibiting particle segregation/pulverisation and agglomeration. Utilizing the particle confinement strategy, we increased the morphological stability of pomegranate structured SnO2 electrocatalysts and demonstrated the reversible nature of the in situ SnO2 reduction. Van Daele, K. et al. Sn-Based Electrocatalyst Stability: A Crucial Piece to the Puzzle for the Electrochemical CO2Reduction toward Formic Acid. ACS Energy Lett. 6, 4317–4327 (2021). Figure 1
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Vassenden, Frode, Torleif Holt, Amir Ghaderi und Arild Solheim. „Foam Propagation on Semi-Reservoir Scale“. SPE Reservoir Evaluation & Engineering 2, Nr. 05 (01.10.1999): 436–41. http://dx.doi.org/10.2118/58047-pa.
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Summary Foam propagation in co-injection of gas and surfactant solution has been studied in a 10-m-long flow apparatus, equipped with pressure ports and fluid sampling valves for every 1 m. The data have been compared to the results of a core scale foam flooding experiment with the same porous medium. The propagation experiments on the 10 m scale revealed that the foam front propagated significantly slower than the injected fluid front. It appeared that foam propagation was not limited by surfactant transport, but was delayed due to the presence of oil in the porous medium. The experiments have been interpreted with the aid of a numerical foam simulator. Introduction Oil is often effectively displaced by gas. Due to the low density and low viscosity of gas, it may be difficult to achieve a good macroscopic sweep efficiency, however. It has been found that the use of foam may reduce gas mobility, and thereby improve the sweep of gas. Foam can be formed within the reservoir when gas and surfactant solution flow together. A successful well treatment with foam is critically dependent on placement of foam to the desired depth in the reservoir. The injection time required to reach a given depth depends on the propagation velocity of the foam. For the design of a foam treatment, prediction of foam propagation becomes an important issue. The aim of the present study was to clarify which mechanisms determine the foam propagation velocity, and to find out how foam propagation on the reservoir scale relates to foam data obtained in conventional coreflood experiments. The literature provides some observations of foam propagation rates at various conditions. At the Kern River steam foam pilot,1 it was found that the formation of one volume of a C16/18 ?-olefin sulphonate (AOS) foam within the formation required injection of 1.5 volumes of surfactant solution and 700 volumes of steam at reservoir conditions. This propagation delay was interpreted as mainly caused by surfactant retention, but it was also suggested that inefficiencies in foam generation and bubble transport could have further slowed down the growth of the foam zone. Also, Irani and Solomon2 observed slow foam propagation, in slim-tube studies of AOS-stabilized CO2 foams. In experiments without surfactant in the slim tube before foam injection, the foam propagated significantly slower than the injected fluid fronts. In experiments with gas slug injection into porous medium presaturated with surfactant solution, piston-like propagation at the velocity of the injected gas front was observed. When oil was present in the porous medium, there was significant propagation delay observed also during gas slug injection, however. In co-injection experiments in cores with the surfactant adsorption already satisfied, Kovscek et al.3 observed piston-like foam propagation with no retardation of a C16/18 AOS foam. Similar observations were made by Osterloh and Jante.4 Kovscek et al. also performed experiments where the core was free from surfactant at the start of foam injection. Then, retardation of the foam front was found, however, demonstrating how surfactant adsorption retards foam propagation. Aarra et al.5 found significant retardation in experiments in cores with residual oil saturation after gas flooding. The cores were presaturated with C14/16 AOS surfactant solution. At a total injection rate of gas and surfactant solution of about 3 m/d (interstitial velocity), the foam propagated with a velocity of 0.036 m/d. In this case, surfactant adsorption cannot explain the slow propagation, and the oil remains the most probable cause for the retardation. Mannhardt and Svorstøl6 also reported slow propagation in systems with surfactant adsorption satisfied. At an injection rate of 1 m/d, the foam used 10 days to propagate the first 40 cm of a core which had 19% pore volume (PV) oil saturation. Without oil, the foam traveled 40 cm in less than half a day, which corresponds approximately to the velocity of the injected fluids. This also points to the oil as one source of propagation delay. At the employed conditions, the foam strength was found to be sensitive to the presence of oil. The literature on oil-free experiments with adsorption satisfied demonstrates that the propagation delay is not intrinsic to foam per se. A quantitative understanding of all effects that control the propagation delay is lacking, however. The present study aims at improving this understanding. The approach taken has been to study foam propagation in well-characterized systems, over large distances (10 m). The porous medium has been characterized by laboratory experiments on the usual core scale, with respect to relative permeability, capillary pressure, and foam flow and surfactant adsorption properties. Then, foam propagation was studied on the semi-reservoir scale, and compared to modeling based on core scale data, in order to learn how to use core data to predict foam propagation in the reservoir. Experiment Flow Apparatus. The semi-reservoir scale flow experiments were carried out at reservoir conditions in a 10-m-long sandpack. The container for the 10 m sandpack was a specially constructed assembly of ten 1 m long tubes made of the corrosion resistant alloy Hastelloy C-276. The outer and inner diameters of the tubes were 25.4 and 18.1 mm, respectively. The 1-m-long tube sections were coupled together with coupling pieces made from the same material. Each coupling piece was equipped with one piston for compression of the sand, one valve for sampling of fluids during flooding, and one port for pressure measurement. Voids in the sand, generated by vibrations during sand filling, were taken up by moving the sand compression pistons. During packing, sand was repeatedly filled at each connection until the pistons could not be moved anymore. This assured that no voids were present at tube connectors. Flow ports and pressure ports were equipped with Hastelloy C-276 wire mesh in order to confine the sand. Each coupling piece changed the direction of flow by 180° such that the entire tube assembly only occupied a volume of 123×40×20 cm3, and could be fitted into a thermostated cabinet. The layout of the apparatus is sketched in Fig. 1. The assembly was designed for a pressure limit of 620 bar at 90°C. Core scale flooding experiments for relative permeability measurements were carried out in a single 1 m section. All flooding experiments were carried out with the tubes oriented horizontally.
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Huh, Chun, und William R. Rossen. „Approximate Pore-Level Modeling for Apparent Viscosity of Polymer-Enhanced Foam in Porous Media“. SPE Journal 13, Nr. 01 (01.03.2008): 17–25. http://dx.doi.org/10.2118/99653-pa.
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Summary Foam is used in the oil industry in a variety of applications, and polymer is sometimes added to increase foam's stability and effectiveness. A variety of surfactant and polymer combinations have been employed to generate polymer-enhanced foam (PEF), typically anionic surfactants and anionic polymers, to reduce their adsorption in reservoir rock. While addition of polymer to bulk foam is known to increase its viscosity and apparent stability, polymer addition to foams for use in porous media has not been as effective. In this pore-level modeling study, we develop an apparent viscosity expression for PEF at fixed bubble size, as a preliminary step to interpret the available laboratory coreflood data. To derive the apparent viscosity, the pressure-drop calculation of Hirasaki and Lawson (1985) for gas bubbles in a circular tube is extended to include the effects of shear-thinning polymer in water, employing the Bretherton's asymptotic matching technique. For polymer rheology, the Ellis model is employed, which predicts a limiting Newtonian viscosity at the low-shear limit and the well-known power-law relation at high shear rates. While the pressure drop caused by foam can be characterized fully with only the capillary number for Newtonian liquid, the shear-thinning liquid requires one additional grouping of the Ellis-model parameters and bubble velocity. The model predicts that the apparent viscosity for PEF shows behavior more shear-thinning than that for polymer-free foam, because the polymer solution being displaced by gas bubbles in pores tends to experience a high shear rate. Foam apparent viscosity scales with gas velocity (Ug) with an exponent [-a/(a+2)], where a, the Ellis-model exponent, is greater than 1 for shear-thinning fluids. With a Newtonian fluid, for which a = 1, foam apparent viscosity is proportional to the (-1/3) power of Ug, as derived by Hirasaki and Lawson. A simplified capillary-bundle model study shows that the thin-film flow around a moving foam bubble is generally in the high-shear, power-law regime. Because the flow of polymer solution in narrower, water-filled tubes is also governed by shear-thinning rheology, it affects foam mobility as revealed by plot of pressure gradient as a function of water and gas superficial velocities. The relation between the rheology of the liquid phase and that of the foam is not simple, however. The apparent rheology of the foam depends on the rheology of the liquid, the trapping and mobilization of gas as a function of pressure gradient, and capillary pressure, which affects the apparent viscosity of the flowing gas even at fixed bubble size. Introduction When a gas such as CO2 or N2 is injected into a mature oil reservoir for improved oil recovery, its sweep efficiency is usually very poor because of gravity segregation, reservoir heterogeneity, and viscous fingering of gas, and foam is employed to improve sweep efficiency with better mobility control (Shi and Rossen 1998; Zeilinger et al. 1996). When oil is produced from a thin oil reservoir overlain with a gas zone, a rapid coning of gas can drastically reduce oil production rate, and foam is used to delay the gas coning (Aarra et al. 1997; Chukwueke et al. 1998; Dalland and Hanssen 1997; Thach et al. 1996). During a well stimulation operation with acid, a selective placement of acid into a low-permeability zone from which oil has not been swept is desired, which can be accomplished with use of foam (Cheng et al. 2002). For environmental remediation of subsurface soil using surfactant, foam is used to improve displacement of contaminant, such as DNAPL, from heterogeneous soil (Mamun et al. 2002).
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Tsubota, Toshiki, Anh Duy Khuong und Daiki Morioka. „(Invited) Performance As Electrode for Electric Double-Layer Capacitor of Activated Carbon Derived from Bamboo Residue after Steam Treatment Activated By Alkaline Metal Hydroxide“. ECS Meeting Abstracts MA2024-02, Nr. 6 (22.11.2024): 703. https://doi.org/10.1149/ma2024-026703mtgabs.
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Introduction Biomass-derived activated carbon can be the electrode material for high performance EDLCs, owing to its high surface area, porosity, and excellent conductivity1). The performance of EDLC electrode can be presumed to depend on pore size distribution from the theory of electric double layer. In Japan, the disorderly expansion of bamboo forest is serious problem because it causes economical damage. Therefore, we have already proposed “cascading usage of bamboo”, the extraction of saccharides by hydrolysis and the usage of solid residue as the precursor for EDLC electrode, as the promising candidate of the solution for the bamboo problem2). The alkaline metal hydroxide, such as KOH and NaOH, is known to be the activator for preparing activated carbon, and the pore size distribution could be presumed to depend on the kind of alkaline metal hydroxide from the proposed activation mechanism. In this study, the solid residue of steam-treated bamboo is used as a precursor for activated carbon for the activation by KOH or NaOH, and the performance as EDLC electrode of the activated carbons is investigated in detail. Experimental Moso bamboo powder and water were separately set in a container for autoclave (HU-100, Sanai Science Co., Ltd.). The container was heated at 200°C for 2.5 hours, which was chosen based on previous work3). The treated bamboo was dispersed in distilled water at room temperature for 1 hour for the extraction of sugars. The solid residue after filtration was heated at 500oC for 1 hour with N2 gas flowing for carbonization. The carbonized sample was mixed with KOH or NaOH, and then the mixture was heated at 800°C for 1 hour with N2 gas flowing. The activated sample washed with heated distilled water for several times and then dried. Raman Spectroscopy (NRS-5100, JASCO Corporation) utilizing a 532 nm laser for excitation was utilized to examine the degree of graphitization within the sample structures. The morphology of the samples was examined by Field Emission Scanning Electron Microscope (FE-SEM) from Japan Electronics Co., Ltd (Model JSM-6701F). The adsorption isotherms of the samples for N2 (at 77 K) and CO2 (at 298 K) was measured by a commercial apparatus (BELSORP-miniII, MicrotracBEL). The electrochemical performance, such as cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and galvanostatic charge/discharge measurement, of the sample was evaluated by using two-electrode cell with 1 M (C2H5)4NBF4 (TEABF4)/PC as electrolyte. Results and Discussions The yield, which is (weight after activation)/(weight before activation), decreased at higher weight ratios of KOH or NaOH, and the yield for NaOH activation was lower than that for KOH activation. The Raman spectra of the samples indicated that the samples have amorphous structure. The SEM images showed that the activated samples kept the microstructure derived from plant tissue. The N2 adsorption isotherms at 77 K for all the activated samples exhibited type I, indicating a microporous structure. However, the NaOH-activated samples displayed gentler slopes at low relative pressure, suggesting wider micropore size distribution. That is, the micropore size distribution depended on the kind of alkaline metal hydroxide. The capacitance values calculated from discharge process at 10 mA g-1 from 2.5-0 V was ca. 25 F g-1, which is comparable to the reported values. The capacitance values calculated from CV curves of NaOH-activated sample, 37.6 F g-1 at 1 mV s-1, was slightly higher than that of KOH-activated sample. Moreover, the decrement of the capacitance value at higher scan rate was trend to be suppressed for NaOH-activated samples. The capacitive contribution calculated according to the Dunn method4) indicated that NaOH-activated carbon showed a higher degree of capacitive contribution (74 %). The wider pore size distribution of NaOH-activated sample could contribute the suppression of the decrement of the capacitance value at higher scan rate. Conclusions The chemical activation by hydroxide of alkaline metal, such as KOH and NaOH, was performed to the solid residue after the extraction of steam-treated bamboo. From the results of the capacitance value, the suppression of the decrement of the capacitance value, and the capacitive contribution, the performance as EDLC electrode of NaOH-activated sample was better than that of KOH-activated sample. The wider pore size distribution for NaOH-activated sample could be one of the reasons for the higher performance. References 1) K.Ö. Köse et al. (2018) International Journal of Hydrogen Energy, 43:18607–16. 2) T. Tsubota et al., (2018) Journal of Porous Materials, 25: 1541-1548. 3) D.A. Khuong et al. (2023) Materials Chemistry and Physics, 304:127853. 4) D. Dubey et al. (2023) Journal of Energy Storage, 58:106441. Figure 1
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Bazan, Antony, Gonzalo García, Angélica María Baena-Moncada und Elena Pastor. „Ni Foam-Supported NiMo Catalysts for the HER“. ECS Meeting Abstracts MA2022-01, Nr. 34 (07.07.2022): 1390. http://dx.doi.org/10.1149/ma2022-01341390mtgabs.
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In the last years, “green hydrogen” fuel had gained a strong relevance due to its potential as friendly-environment energy source to replace fossil fuels. “Green hydrogen” fuel is obtained from water splitting by electrolysis, which can be powered by renewable energy sources, avoiding the emission of CO2 gas as by-product [1]. Particularly, alkaline water splitting has been, extensively, reported as the most sustainable and low-cost route for “green hydrogen” production. However, either oxygen (OER) or hydrogen evolution (HER) half-reaction can be limited by low-relative abundance of noble metals used as commercial electrocatalysts, such as, the benchmarking IrO2||Pt two-electrode couple of 1.57 V at 10 mA cm-2 [2]. Hence the design of non-noble electrocatalysts has gained relevance due to their remarkable electroactivity and high abundance. Mainly, Ni, Fe, Co and/or Mo - based electrocatalysts showed outstanding performance toward the HER. Indeed, theoretical studies indicated that their metallic surfaces promote the hydrogen electro-adsorption as like-metal hydride [M-H], hydroxide [M-OH] and or oxyhydroxide [MOOH] species [3–5]. Consequently, a controlled charge transfer in a two-step mechanism allows a fast electroreduction of water to the desired “green hydrogen” gas. Herein, we report the synthesis of bimetallic nanostructures, which are produced by thermal-controlled chemical reduction of their precursor salts (NiCl2, Na2MoO4) on the activated nickel foam (NiFA) surface at different highest temperatures (60, 70 and 80 ºC) [4,6]. Therefore, electrocatalysts were labeled as NiMo60/NiFA (60ºC), NiMo70/NiFA (70 ºC) and NiMo80/NiFA (80 ºC). Materials were physicochemical characterized by XRD, SEM, ICP-MS, infrared and Raman spectroscopy, and the HER on the synthesized catalysts in alkaline media was monitored by Differential Electrochemical Mass Spectrometry (DEMS) and in-situ Raman spectroscopy (Fig. a-d). Main results reveal outstanding electrochemical performance toward the HER on the novel nanomaterials, which is mainly influenced by the highest temperature reached at the synthesis procedure. Furthermore, DEMS indicate similar reaction mechanism for the HER at all catalysts and an increment of the catalytic activity rising the temperature at the synthesis stage. References Germscheidt RL, Moreira DEB, Yoshimura RG, Gasbarro NP, Datti E, dos Santos PL, et al. Hydrogen Environmental Benefits Depend on the Way of Production: An Overview of the Main Processes Production and Challenges by 2050. Adv Energy Sustain Res. 2021;2(10):2100093(1-20). Li X, Zhao L, Yu J, Liu X, Zhang X, Liu H, et al. Water Splitting: From Electrode to Green Energy System. Nano-Micro Lett. 2020;12(1):1-29 Abbas MA, Bang JH. Rising Again: Opportunities and Challenges for Platinum-Free Electrocatalysts. Chem Mater. 2015;27(21):7218–7235. Nairan A, Zou P, Liang C, Liu J, Wu D, Liu P, et al. NiMo Solid Solution Nanowire Array Electrodes for Highly Efficient Hydrogen Evolution Reaction. Adv Funct Mater. 2019;29(44):1903747(1–8). Chen G, Wang T, Zhang J, Liu P, Sun H, Zhuang X, et al. Accelerated Hydrogen Evolution Kinetics on NiFe-Layered Double Hydroxide Electrocatalysts by Tailoring Water Dissociation Active Sites. Adv Mater. 2018;30(10):1706279(1-7). Cao J, Li H, Pu J, Zeng S, Liu L, Zhang L, et al. Hierarchical NiMo alloy microtubes on nickel foam as an efficient electrocatalyst for hydrogen evolution reaction. Int J Hydrogen Energy. 2019;44(45):24712–247128. Acknowledgments The Peruvian Fund for Science and Technology (PROCIENCIA) and the Peruvian Minister of Education (MINEDU) by supporting the present work under project 298-2019 FONDECYT and the Doctoral Program with contract 237-2015. The Spanish Ministry of Economy and Competitiveness (MINECO) under project ENE2017-83976 -C2-2-R (FEDER) (co-funded by FEDER). G.G. acknowledges the “Viera y Clavijo” program (ACIISI & ULL), NANOtec, INTech, and Cabildo de Tenerife for laboratory facilities. Authors would like to acknowledge the use of SEGAI—ULL facilities. Figure 1
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Ooka, Chie, Yuta Nakayasu, Shu Sokabe, Tomoya Yamada, Naoka Nagamura, Kenichi Ozawa und Masaru Watanabe. „An Aqueous Organic Redox Supercapacitor Fabricated By Supercritical CO2 Impregnation of Quinones into Activated Carbon“. ECS Meeting Abstracts MA2024-02, Nr. 67 (22.11.2024): 4501. https://doi.org/10.1149/ma2024-02674501mtgabs.
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The aqueous organic redox supercapacitor (OSC) is a metal-free, safe, and cost-effective energy storage device.[1] It utilizes activated carbons (AC) impregnated with two types of quinones as electrodes and an aqueous solution as the electrolyte. The redox reaction of quinones serves as the electron carrier. Conventional liquid impregnation methods for loading quinones onto AC have been used but such methods are limited by low quinone loading ratios and low specific capacities. In this study, a supercritical fluid (SCF) impregnation method is proposed to improve the quinone loading and the energy density of OSC. All OSC fabricated via this method were evaluated, and the impregnation effects compared with those in liquid impregnation method through thermogravimetric analysis (TG) and X-ray absorption fine structure (NEXAFS) measurements. The cathodes were fabricated by placing AC and tetrachloro-1,4-benzoquinone (TCBQ) in a tube reactor, maintaining them at 105°C and 15 MPa for 24 hours, as per previous study.[2] The anodes were prepared by placing AC, 1, 5-dichloroanthraquinone and ethanol in a reactor and holding the mixture at 155°C and 25 MPa for 24 hours. For comparison, liquid impregnation method was used to fabricate respective electrodes.[1] The quinone loading in each sample was assessed through TG analysis while the electrochemical measurements were performed using a 0.5 mol/L sulfuric acid solution as the electrolyte. Specific capacities of half-cell (1A/g, -0.3-0.3V vs Ag/AgCl) and full cell (2A/g, 0-1.2V) configurations were determined via constant current measurements using a galvanostatic. Additionally, the quinone loading on AC surface of each sample was investigated using the NEXAFS method. In comparison with the liquid impregnation method, cathodes and anodes produced through SCF impregnation exhibited a 37% and 83% increase in specific capacity, respectively. This enhancement was attributed to the amplified impregnation and loading of redox molecules. The superior solubility of redox molecules in supercritical CO2, along with its high diffusion and low viscosity, facilitated the impregnation and loading of redox molecules into the micropores of the porous carbon. In fact, TG analysis results showed that the supercritical quinone loading was higher in the supercritical impregnation method than in the liquid impregnation method, and the correlation between quinone loading and electrode properties was confirmed. Overpotential suppression was also confirmed, suggesting a decrease in interfacial resistance due to improved adsorption morphology.[3] Full cell measurements showed an energy density of 21 Wh/kg, 1.4 times higher than previous studies.[1] In a durability test of 1000 cycles, the energy density retention rate was 95%, indicating excellent electrode properties with high capacity and long life. Comparing the OSC properties in this study to other energy storage devices, the OSC performed higher than nickel-cadmium and lead-acid batteries for energy density and power density, and higher than cobalt-based lithium-ion batteries in terms of power density.[4] In the K-edge NEXAFS spectra of carbon, the transition peak to the 1s→π* orbital derived from TCBQ[5] was observed at a higher energy in the SCF impregnation compared to the in liquid impregnation. In this case, the peak appeared at a higher energy level due to the strong interactions between the TCBQ supported by the SCF impregnation and AC resulting in the increase in the ratio of π-bonded components and hence an increase in the effective oxidation number. References Tomai et al., Sci. Rep.,4, 3501(2014) Nakayasu et al., Chem. Commun.,59, 3079(2023) N. Tisawat et al., Appl. Surf. Sci., 491, 784–791(2019) S. Sarmah et al., WIREs Energy Environ., 01, 461(2022) SC. Ray et al., Sci. Rep., 4, 3862(2014)
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Carpenter, Chris. „Locally Produced Sustainable and Resilient Surfactants for Enhanced Oil Recovery“. Journal of Petroleum Technology 76, Nr. 11 (01.11.2024): 86–88. http://dx.doi.org/10.2118/1124-0086-jpt.
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_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 24518, “Locally Produced Sustainable and Resilient Surfactants for Enhanced Oil Recovery,” by Syed Muhammad Shakil Hussain, SPE, Muhammad Shahzad Kamal, SPE, and Afeez Gbadamosi, King Fahd University of Petroleum and Minerals, et al. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ Chemical flooding is a major enhanced oil recovery (EOR) method for recovering residual oil within rock pores. Injected chemicals such as surfactant, however, must be soluble in low- and high-salinity brine, compatible with reservoir ions, and stable at elevated temperatures. The main objective of the study described in the complete paper is to explore the potential of locally produced surfactants for EOR in high-temperature and high-salinity reservoir environments. Design and synthesis of the new surfactants were achieved using green or no solvents. Importance of Chemical EOR Because only 15–20% of hydrocarbons can be extracted in the primary recovery stage, the waterflooding or gas-injection techniques usually are applied in the secondary recovery stage to extract 15–20% more oil and maintain the oilfield’s original pressure. After the application of these two techniques, however, a large amount of oil remains, the extraction of which requires the use of EOR, which can include thermal, gas, or chemical techniques. In thermal EOR, hot water or steamflooding are usually used to recover heavy oil. Currently, other thermal EOR methods such as in-situ combustion or steam-assisted gravity drainage receive considerable attention, especially in reservoirs containing heavy to extra-heavy crude oil. Gas methods normally are used in reservoirs featuring light and volatile oil. CO2 flooding is perhaps the most extensively applied gas EOR method for light oil extraction. Other gases such as nitrogen, hydrocarbon gas, acid gas, and air also are used for oil recovery. Chemical EOR involves the injection of chemicals including surfactants, polymers, alkali, and mixtures thereof. The polymer tends to increase the viscosity of the aqueous phase and lower the permeability of reservoir rocks. Surfactants minimize the interfacial tension (IFT), cause emulsification, and alter the wettability of the reservoir rocks. Alkali flooding generates in-situ surfactant by reacting with organic acid and ultimately reducing the IFT. Surfactants are organic compounds having both lipophilic and lipophobic parts. The lipophilic part is called a nonpolar compound and is soluble in the oil phase. The lipophobic part is termed a polar group and is soluble in the aqueous phase. Because of the availability of both lipophilic and lipophobic compounds in the same chemical structure, the surfactant stays on the interface of the water and oil phase and reduces the IFT. Based on the charge of the lipophobic head, the surfactants can be classified as nonionic, cationic, anionic, and zwitterionic (Fig. 1). Each class of surfactants possesses unique properties. For example, anionic surfactants are the material of choice in sandstone reservoirs because of their low adsorption into reservoir rocks. Similarly, the cationic surfactants exhibit minimum adsorption in carbonate rocks because of charge repulsion. Zwitterionic surfactants (ZS) show high heat-stability and salt-tolerance properties, and nonionic surfactants are known for their use as cosurfactants or solvents.
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Dominguez-Benetton, Xochitl. „(Invited) Lithium Recovery from Geothermal Brines“. ECS Meeting Abstracts MA2022-02, Nr. 27 (09.10.2022): 1040. http://dx.doi.org/10.1149/ma2022-02271040mtgabs.
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Lithium is a critical raw material for developing current lithium-ion batteries and prospective next-generation batteries. Its reserves are concentrated in a handful of countries. It is primarily extracted from continental brines, wherein Li+ is relatively concentrated (0.3 –1.5 wt%) in a complex mixture of many more components with relatively large water solubilities. Current practices to extract lithium from continental brines involve evaporation, i.e., >90% of water. Eventually, the concentration of Li+ intensifies up to 6–7%, in a brine which follows numerous chemical processing steps, to ultimately produce battery-grade lithium chemicals. Despite being the easiest and currently most cost-effective practices, these are inefficient and unsustainable (chemical-intensive, requires extensive land use and time, and delivers large volumes of waste), especially in the context of the sharp increase in the demand for lithium that is already happening and is expected to endure in the coming decades. To sustainably meet the future demand for lithium, it is imperative to develop more efficient extraction methods, which are faster, less climate/weather reliant, minimize waste production, and especially deal with water differently than current industrial processing (i.e., circumventing evaporation). Besides being applicable to concentrated lithium brines, characteristic of primary extraction, these methods should especially be applicable to dilute brines (i.e., geothermal, oilfield, seawater, wastewater,—which contain 0.01–0.3 mg of Li+ per L of brine), as these have more recently prospected for Li recovery. Together with lithium recycling from spent batteries, these hold the promise of delocalizing raw lithium sourcing. New extraction technologies have emerged within the past decade, including adsorption and the use of membranes. In addition to being insufficient for an effective recovery, some alternatives seem to imply a harsher environmental impact than current practices, whereas others would be disadvantageous to treat the large volumes of fluid associated with lithium extraction. Especially, electrochemical methods for Li+ recovery are (re)surging.[1] The use of Li+ insertion electrodes coupled to membranes and membrane electrolysis are notoriously thriving.[1,2] However, the first approach bears the limitation of requiring extremely thin and large area electrodes to process large brine volumes, and the second one suffers from being energy-intensive, plus current investigations show the constant addition of chemicals for pH adjustment, and produce chloride- and hypochlorite-anions rich solutions which are neither economic nor sustainable.[2] Furthermore, in membrane electrolysis swelling of the ion exchange membrane could be an issue[3] that has not been addressed in Li+ recovery studies; if excessive, this could lead to membrane deformations and ultimately to the blockage of the flow channels within the reactor. Despite the aforementioned limitations, electrochemical methods are a more sustainable and versatile option, with latent competitiveness vs. current industrial practices. Thus, ideal solutions should have the added value of circumventing the limitations of the state-of-the-art electrochemical approaches mentioned above. This aim was pursued in the present work. Gas diffusion electrodes (GDEs) are broadly used in electrochemical energy-conversion devices, such as fuel cells and metal-air batteries, as well as in electrolyzers aiming at chemical synthesis, like in the chlor-alkali industry, hydrogen peroxide production, CO2 conversions to fuels and fine chemicals, or N2 reduction to ammonia. Recently, the use of GDEs was pioneered for metal recovery in a process named gas-diffusion electrocrystallization (GDEx).[4–7] This talk will explain the underlying principles of GDEx and its successful application in the recovery of highly dilute lithium (<300 mg L-1) in synthetic brines containing up to 150 mg L-1 NaCl, as well as in real geothermal brines with Li+ concentrations below 50 mg L-1. Up to 50% of direct lithium extraction from the brine can be achieved, selectively, forming solid materials with lithium concentrations >0.5%, which are promising as a starting material for the direct conversion into battery-grade lithium hydroxide or carbonate. References: [1] Battistel A., et al. (2020) Adv Mater 32, 1905440. [2] Torres W.R., et al. (2020) J Membrane Sci, 615, 118416. [3] Paidar, M., Faleev V., Bouzek K. (2016) Electrochim Acta, 209, 737. [4] Prato et al. (2019) Sci Rep https://doi.org/10.1038/s41598-019-51185-x [5] Prato et al. (2020) J Mat Chem A https://doi.org/ 10.1039/D0TA00633E [6] Pozo et al. (2020) Nanoscale https://doi.org/10.1039/C9NR09884D [7] Eggermont et al. (2021) React Chem Eng https://doi.org/10.1039/D0RE00463D Acknowledgements: This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654100 (CHPM2030 project). Support from the Flemish SIM MaRes programme, under grant agreement No 150626 (Get-A-Met project) is also acknowledged. The author thanks Elisabet Andres Garcia, Luis Fernando Leon Fernandez and Erwin Maes for their valuable contributions to this work.
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Setka, Milena, Albert Behner, Milutin Smiljanic, Marjan Bele, Nejc Hodnik und Miroslav Šooš. „Microwave-Assisted Synthesis of Nitrogen-Doped Carbon Catalysts for Oxygen Reduction Reaction with Tunable Selectivity“. ECS Meeting Abstracts MA2023-02, Nr. 9 (22.12.2023): 1029. http://dx.doi.org/10.1149/ma2023-0291029mtgabs.
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The oxygen reduction reaction (ORR) is the core reaction in electrocatalysis systems such as fuel cells, metal-air batteries and hydrogen peroxide (H2O2) electro-generation. The ORR reaction mechanism has two possible pathways, namely, two-electron (2e−) or four-electron (4e−) processes that enable a reduction of oxygen into H2O2 or water (H2O), respectively. Both paths are useful where the former can provide on-site direct production of H2O2 and the latter is desired in fuel cells and batteries since it enables higher energy efficiency. Optimal ORR electrocatalyst should exhibit high activity, selectivity, stability, and low cost. Carbon materials modified with heteroatoms (e.g. nitrogen (N)) are considered potential alternatives for costly noble metal catalysts including Pt for ORR in fuel cells, and Au for the ORR to H2O2 (1,2). The typical synthesis procedure for the porous nitrogen-doped carbons (N–C) is based on the single or multiple pyrolysis steps of nitrogen-rich carbon precursor. The reactions required a pyrolysis step at the temperature range of 500-1200 °C and timing of one to tens of hours. Such processes showed a highly negative environmental impact due to high energy consumption. The production of 1 ton of activated carbon from lignocellulosic biomass feedstock requires 669.83 kWh (equivalent to an emission of 62.78 tons of CO2) (3). The synthesis of the N–C by microwave (MW) irradiation can reduce energy usage and ensure a more environmentally sustainable and economically viable approach. This procedure necessitates non-transparent materials to electromagnetic waves that can convert MW energy into heat and simultaneously enable the carbonization of the starting material. This work investigated the electrocatalytic activity towards ORR for N–C–MW catalysts derived from polyaniline (PANI) prepared in a one-step MW carbonization approach. PANI was selected due to two reasons: (i) N–C made by thermal pyrolysis of PANI showed improved electrocatalytic activity toward ORR where both the 4e− and the 2e− electron transfer pathways are feasible depending on the nature of active sides (4), (ii) PANI displayed good MW adsorption properties (5). The work aimed to identify the influence of the MW reaction condition on the resulting structure of the N–C–MW and the direction of the ORR. The N–C–MW samples were prepared under MW power of 450 and 800 W and time of 70, 140 and 210 s. The ORR activity of N–C–MW samples was investigated by cyclic voltammetry in the alkaline media (O2-saturated 0.1 M KOH). The experiment was performed in a three-electrode configuration composed of a rotating ring (Pt)–disk (glassy carbon) electrode (RRDE), a graphite rod as the counter electrode and a reversible hydrogen electrode (RHE) as the reference electrode. An influence of catalyst loading on disk electrode (0.05, 0.1 and 0.2 mg/cm2) was analyzed. All investigated MW reaction conditions resulted in the formation of porous disordered carbon structures with nitrogen and oxygen functionalities confirmed by X-ray photon-electron spectroscopy. The shorter time (70 s) and lower power (450 W) of MW treatment resulted in the formation of structures with a low carbonization rate and simultaneously a relatively poor catalytic activity for ORR (an onset potential of ∼0.65 V vs RHE). The samples carbonized under moderate (power of 450 W and 800 W, time of 140 s) and severe (power of 450 W, time of 210 s) reaction conditions showed higher selectivity to H2O2 or water H2O, respectively. The selectivity of 80 % to H2O2 was achieved for the N–C–MW-800W-140s sample at the potential of 0.6 V vs RHE at the catalyst loading of 0.05 mg/cm2. The results showcase the potential of MW carbonization in producing ORR electrocatalysts with diverse functionalization, leading to modified reaction selectivity that can be utilized in various electrocatalytic applications. Acknowledgments The research leading to these results was supported by the Johannes Amos Comenius Programme, European Structural and Investment Funds, project 'CHEMFELLS V‘ (No. CZ.02.01.01/00/22_010/0003004). References Yang, S. et al., Toward the decentralized electrochemical production of H2O2: A focus on the catalysis. ACS Catalysis, 2018. Bouleau, L. et al., Best practices for ORR performance evaluation of metal-free porous carbon electrocatalysts. Carbon, 2022. Wang, YX. et al., Quantifying environmental and economic impacts of highly porous activated carbon from lignocellulosic biomass for high-performance supercapacitors. Energies, 2022. Silva, R. et al., Efficient metal-free electrocatalysts for oxygen reduction: Polyaniline-derived N- and O-doped mesoporous carbons. Journal of the American Chemical Society, 2013. Oyharçabal, M. et al., Influence of the morphology of polyaniline on the microwave absorption properties of epoxy polyaniline composites. Composites Science and Technology, 2013. Figure 1
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Halim, El Mahdi, Lisa Pierinet, Rémi Blanchard, Maidhily Manikandan, Thi bich hue Tran, Micah Barker, Janith Kariyawasam, Fanny Tricot und Julien Durst. „Electrode Coating Process Impact on the Performance of Pt and PtCo Fuel Cell Cathode Catalysts“. ECS Meeting Abstracts MA2023-02, Nr. 40 (22.12.2023): 1983. http://dx.doi.org/10.1149/ma2023-02401983mtgabs.
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The polymer electrolyte membrane fuel cell (PEMFC) is one of the most promising energy sources for replacing fossil fuels in vehicles, as it does not produce greenhouse gas emissions during operation. As a key player in hydrogen mobility, SYMBIO is developing and producing PEMFC systems for a large field of applications. SYMBIO masters the electrochemical core (the Membrane Electrode Assembly - MEA), the complete stack (bipolar plate, stacking and housing) and the fuel cell system (Balance of Plant, operating conditions, control-command, packaging) [1]. The widespread use of fuel cell vehicles is strongly linked to the price of the PEMFC system, in which the MEA as a high share. Decreasing the total PGM content, as well as moving to high-speed roll-to-roll production methods are important levers in the cost roadmap of MEAs. And from a performance point of view, systems for the heavy-duty market will need to show high efficiencies at low current densities (<1 A/cm2). Exploring the potential of highly active cathode catalyst is therefore mandatory for these applications. State of the art cathode catalyst layers consists in either Pt or PtCo-alloy supported on carbon material, the latter being more active for the ORR but also less resistant towards potential cycling. Regarding the ink formulation, the use of PtCo poses the challenge that Co atoms could dissolve, even if the catalyst has been previously acid leached, leading to the release of free Co2 +. These free ions will latter lower the catalytic activity and the transport of reactants (H+ and O2) to the active sites in the catalytic layer [2-3]. The manufacturing of a catalyst coated membrane (CCM) can be done with different printing processes involving a catalytic ink and a substrate. Each coating process has different constraints (ink rheological behaviour, particle size) leading to optimisation of ink recipe (solvent matrix, solid content ...). The ink must also be compatible with the substrate that can be directly an MEA component such as the membrane (direct coating) or the GDL, or a decal-carrier substrate. All these parameters lead to catalyst layer structure differences that impact the MEA performance. In this study, the impact of three coating processes, hence three solvent systems for a same catalyst, ionomer, and I/C ratio, on the MEA performance is explored for commercial Pt and PtCo catalysts. The coating processes compared are direct coating on membrane via bar coater and spray coater and non-direct coating using decal method. The inks properties including the granulometry and the viscosity of different prepared inks were characterized before coating. Ex-situ techniques (SEM-EDX, TEM, N2 adsorption/desorption) were used to figure-out the impact of the coating process on the morphology and porosity of the cathodic catalyst layer. The influence of these parameters on the electrochemical performance was studied using H2-Air polarization curves, electrochemical impedance spectroscopy and the electrochemical surface area (ECSA). It will be highlighted how important the final PEMFC performance must be understood by taking into account the used ink system and coating process, as well as the intrinsic stability of catalyst, ionomer and membrane during these stages. References [1] www.symbio.one [2] Nagappan Ramaswamy et al 2021 J. Electrochem. Soc. 168 024519 [3] Deborah J. Myers et al 2021 J. Electrochem. Soc. 168 044510
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Markunas, Brianna, und Joshua David Snyder. „pH Driven Pathways to Promote the Electrochemical Hydrogenation of Phenol and Other Aromatic Hydrocarbons“. ECS Meeting Abstracts MA2022-02, Nr. 52 (09.10.2022): 1999. http://dx.doi.org/10.1149/ma2022-02521999mtgabs.
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The electrochemical hydrogenation (ECH) of bio-mass derived compounds is an attractive alternative to traditional thermochemical hydrogenation (TCH) methods that are used in the U.S. chemical and petroleum industries to produce value-added fuels and chemicals. TCH uses high pressures and temperatures, along with an external source of hydrogen gas typically produced via methane reformation; these requirements make it an energy intensive process. ECH has the advantages of operating near ambient conditions and sourcing the participating hydrogen from the aqueous electrolyte solution, resulting in reduced energy costs and CO2 emissions compared to TCH. The applied potential provides an additional parameter for controlling selectivity, which makes ECH more suitable to handle the wide chemical variability of biomass-derived feedstocks. Aromatic hydrocarbons are of interest as model compounds for lignocellulosic bio-oil [1]. The ECH of aromatic hydrocarbons proceeds with high faradaic efficiency (FE) at low overpotentials, however, the ECH turnover rate remains low at these potentials. There is no simple fix to this, as any increase in overpotential, to increase ECH rate, will reduce the reaction FE due to competition with the hydrogen evolution reaction (HER). In this work we address the need for a more fundamental understanding of ECH systems to promote high turnover rates at low overpotentials. Specifically for phenol TCH, it is well known that the hydrogenation is limited by the formation/addition of surface adsorbed hydrogen. The current ECH literature draws on these TCH studies and assumes that phenol ECH is also limited by surface adsorbed hydrogen [2]. Thus, most ECH work is done is acidic media, where the kinetics of surface adsorbed hydrogen formation are fastest on platinum [3]. HER, however, is also faster on platinum in acidic media [4], making it more difficult to achieve high faradaic efficiency. Because of this limited scope of investigation, the impact of electrolyte chemistry, i.e. pH, on ECH kinetics has only been sparingly investigated. In this work, we investigate a new pathway for enhanced rates at low overpotentials, driven by the acid-base chemistry of reactants and using electrolyte pH to promote dissociative adsorption. By tailoring the electrolyte pH based on the pKa of the reactant molecule, we can lower the barrier associated with the first hydrogenation step, improving overall reaction kinetics. We demonstrate this effect with phenol ECH at various pH electrolyte on low-index single crystal electrodes using rotating disk electrode voltammetry and chrono-amperometry with product analysis. The ECH of acetophenone and benzaldehyde are also included to compare the effect of different functionalities on the phenyl ring. We report on the structural sensitivity, influence of pH and resulting electric field effects, and present new mechanistic insights for phenol ECH. With these insights we propose methods to promote higher ECH rates at lower overpotentials. References: [1] J. Yan et al., "Characterizing Variability in Lignocellulosic Biomass: A Review," ACS Sustainable Chemistry & Engineering, vol. 8, no. 22, pp. 8059-8085, 2020, doi: 10.1021/acssuschemeng.9b06263. [2] N. Singh et al., "Aqueous phase catalytic and electrocatalytic hydrogenation of phenol and benzaldehyde over platinum group metals," Journal of Catalysis, vol. 382, pp. 372-384, 2020, doi: 10.1016/j.jcat.2019.12.034. [3] S. Intikhab, J. D. Snyder, and M. H. Tang, "Adsorbed Hydroxide Does Not Participate in the Volmer Step of Alkaline Hydrogen Electrocatalysis," ACS Catalysis, vol. 7, no. 12, pp. 8314-8319, 2017, doi: 10.1021/acscatal.7b02787. [4] I. Ledezma-Yanez, W. D. Z. Wallace, P. Sebastián-Pascual, V. Climent, J. M. Feliu, and M. T. M. Koper, "Interfacial water reorganization as a pH-dependent descriptor of the hydrogen evolution rate on platinum electrodes," Nature Energy, vol. 2, no. 4, 2017, doi: 10.1038/nenergy.2017.31.
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Martinez Mora, Omar, Luis F. Leon-Fernandez, Jan Fransaer und Xochitl Dominguez-Benetton. „Enhancing Direct Methanol Oxidation with Pt-Pd Alloy Nanoparticles Synthesized By Gas Diffusion Electrocrystallization (GDEx)“. ECS Meeting Abstracts MA2023-02, Nr. 41 (22.12.2023): 2045. http://dx.doi.org/10.1149/ma2023-02412045mtgabs.
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Direct methanol fuel cells (DMFCs) are a promising sustainable energy solution due to their high energy density, low-temperature operation, and portability. However, sluggish methanol oxidation reaction (MOR) kinetics hinders their successful commercialization.1,2 Pt is a highly active MOR catalyst due to its ability to adsorb and decompose methanol on its surface. However, when pure Pt is used, the adsorption of oxidation intermediaries, i.e., CO, occurs, blocking catalytically-active sites and reducing the catalytic efficiency.2 A promising strategy to improve the catalytic activity and CO tolerance of Pt is by alloying. Among several candidates, Pd stands out due to its identical crystal structure and similar lattice constant to Pt, resulting in single-phase bimetallic materials with strong coupling and improved catalytic performance. In addition, the active surface area is enhanced, and stability is improved by using Pt-Pd alloys.3 We recently reported an electrochemical method for synthesizing platinum group (PGMs, i.e., Pt, Pd, Rh) nanoparticles (NPs) using Gas-Diffusion Electrocrystallization, best known as the GDEx process.4 In GDEx, CO2 and water are reduced using a gas diffusion electrode, producing CO and H2, which in turn reduce PGMs ions in solution, forming metal nanoclusters of 10 nm–40 nm composed of even smaller nanocrystals of 2 nm–4 nm. In this work, we used GDEx to synthesize Pt-Pd alloy NPs with different metal ratios (Pt100, Pt75-Pd25, Pt50-Pd50, Pt25-Pd75 and Pd100). The Pt-Pd alloy NPs were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy. The size distribution of the synthesized nanomaterials was between 15 nm–30 nm, increasing in size with increasing Pd content. The catalytic activity of the Pt-Pd alloy NPs toward methanol oxidation was measured in 0.1 M HClO4. The electrochemical surface area (ECSA), measured by the Cu underpotential deposition method,5 was 37.1 ± 2.1, 36.1 ± 2.7, 42.5 ± 1.7 and 56.1 ± 2.9 m2 gPt -1 for Pt100, Pt75-Pd25, Pt50-Pd50, and Pt25-Pd75 respectively. The mass activity (MA, fig.1a), defined by the current density per unit mass of Pt loading at the forward peak, was 452 ± 10, 345 ± 16, 365 ± 21 and 189 ± 15 for Pt100, Pt75-Pd25, Pt50-Pd50, Pt25-Pd75. Even though the MA for Pt75-Pd25 and Pt50-Pd50 was lower than for Pt100, their onset potential was smaller (0.503 VRHE for Pt75-Pd25 and 0.488 VRHE for Pt50-Pd50) than for Pt100 (0.530 VRHE) indicating that the MOR is more favourable on those alloys. Besides, during the accelerated stability test (ADT, Fig.1b), after 1000 cycles, Pt75-Pd25 and Pt50-Pd50 showed higher stability and resistance towards CO poisoning than Pt100 by holding 80% and 70% of their peak current density. In comparison, Pt100 only kept ∼60% of its peak current density under the same conditions. In summary, the GDEx process allows the synthesis of Pt-Pd alloy NPs with a similar or superior catalytic performance towards MOR than pure Pt NPs, i.e., similar MA but with a better tolerance towards CO poisoning. The selectivity of the GDEx process for PGMs allows the synthesis of Pt-Pd catalysts for DMFCs not only from synthetic solutions but also from complex matrixes that contains a mixture of both PGMs (i.e., leachates from spent automotive catalytic converters). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements No. 958302 (PEACOC project) and No. 101091715 (FIREFLY project). Yuda A, Ashok A, Kumar A. Catalysis Reviews. 2022;64(1):126-228. Ren X, Lv Q, Liu L, Liu B, Wang Y, Liu A, Wu G. Sustain. Energy Fuels. 2020;4(1):15-30. Yousaf AB, Imran M, Uwitonze N, Zeb A, et al. J . Phy s. Chem . C. 2017;121(4):2069-79. Martinez-Mora O, Pozo G, Leon-Fernandez LF, Fransar J, Dominguez-Benetton X., RSC Sustain. 2023; DOI: 10.1039/D3SU00046J. Green CL, Kucernak A. J. Phys. Chem. B. 2002;106(5):1036-47. Figure 1
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LI, Xin, und Michael K. H. Leung. „Efficient Synthesis of Nitric Acid Under Air Atmosphere with Lattice-Confined Ru Clusters“. ECS Meeting Abstracts MA2023-02, Nr. 57 (22.12.2023): 2781. http://dx.doi.org/10.1149/ma2023-02572781mtgabs.
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Nitrate (NO3 -) is an important industrial chemical used as fertilizers in agriculture, as well as oxidizing agents in explosives. Today, NO3 - is manufactured predominantly via an Ostwald process by oxidizing ammonia (NH3), and the ammonia used here comes primarily from the Haber–Bosch (HB) process.However, this process operates at high temperatures (300–500 °C) and pressures (200–300 bar), and requires a coupled steam reforming plant for hydrogen (H2) production. As a result, approximately 1.9 metric tons of CO2 is formed per metric ton of NH3 produced, contributing significantly to climate change. In addition, due to the complexity of the Ostwald and Haber-Bosch processes, it is only economical at large scales, leading to centralized production, which situation is poorly matched with the distributed nature of HNO3 utilization. Therefore, it is highly desirable to bypass the ammonia route and develop a direct and sustainable approach for HNO3 synthesis. Electrochemical synthesis of chemicals has been regarded as an attractive alternative to traditional thermochemical methods. In electrochemical reactions, electric potential can replace high temperature and pressure as the thermodynamic driving force.Therefore, direct electrochemical oxidation of molecular nitrogen appears to be a very potential approach for HNO3 synthesis,which could be sustainable, modular and easily integrated with intermittent renewable electricity. However, due to the lack of natural or artificial electrocatalysts as a reference, the nitrogen oxidation reaction (NOR) remains largely unexplored despite its enormous practical value as a replacement for the fossil fuel-driven two-step HNO3 preparation approach.Until 2019, Zhang et al. reported the first experimental NOR electrocatalyst composed of well-dispersed Pd nanoparticles on MXene nanosheets that can effectively convert N2 into nitrate, which definitely proved the feasibility of using electrochemistry to motivate the endothermic NOR at ambient conditions. Unfortunately, to date, there are still only a few works that reported the electrosynthesis of nitrate from nitrogen, and the proposed electrocatalysts can only achieve limited NOR activity. An in-depth exploration of the NOR process, which consists of two main steps: the first step is a rate-limiting step that converts inert N2 into the active NO* intermediate; the second step is a nonelectrochemical step where NO* reacts with H2O and the generated O* from electrocatalytic water splitting to form nitrate. Therefore, the main factors restricting the development of the electrochemical nitrate synthesis technology can be inferred as follows: (1) the strong N≡N triple bond in the dinitrogen molecule (bond energy: 940.95 kJ mol−1) is highly challenging to oxidate nitrogen to nitrate under mild conditions; (2) the potential window between the NOR and oxidation evolution reaction (OER) is quite narrow, and thus the latter as a competitive reaction can severely restrict the selectively of the nitrogen oxidation synthesis of nitrate; (3) the extremely low solubility and diffusion coefficient of N2 in aqueous electrolytes can significantly inhibit the nitrogen available for the reaction, resulting in unfavorable NOR performance. Therefore, to overcome the above obstacles, extensive studies should focus on designing efficient nitrogen oxidation catalysts and improving electrochemical reaction systems to promote NOR and suppress OER. In the present work, we firstly discovered that synthesizing Ru particles grow along the TiO2 lattice (Ru-TiO2) as the working electrode and can achieve excellent NOR performance by using air as a gas source. Textural analysis sufficiently demonstrates that the matching lattice constants of metal Ru and TiO2 allow the Ru to be confined in the TiO2 lattice, leading to the formation of Ru-Ti bonds and the transfer of electrons from TiO2 to Ru metal. Our results reveal that the electron redistribution of Ru-TiO2 can significantly alter the electronic structure of Ru, leading to the formation of highly occupied Ru 4d bands, which can effectively change the adsorption of surface species and improve the NOR activity. In addition, the Ru confined in TiO2 exhibits particularly high stability towards NOR up to potentials above 1.7 V (versus RHE). As a result, Ru-TiO2 could achieve a record-high NOR performance with a nitric acid yield rate of 18.71 ug h-1 cm-2 (150.2 μmol h-1 g-1) and Faraday efficiency of 25.17% in the air atmosphere. This discovery suggests that the surface oxophilicity and electronic structure of metal particles can be effectively modified by lattice confinement in semiconductors and offers an alternative concept for designing catalysts with unique properties for use in catalysis and beyond. Figure 1